Lithium metal rechargeable battery

Abstract

To improve the reversibility of the negative electrode reaction.SOLUTION: A lithium metal secondary battery includes a power generating element and an electrolyte. The power generating element includes a positive electrode and a negative electrode. The negative electrode includes a substrate and a protruding portion. The substrate is conductive. The protruding portion is insulating. A recess is formed on the surface of the substrate. The protruding portion is disposed on the surface of the substrate. The protruding portion protrudes outward from the surface of the substrate. The relationship of the formula "0.001≤d / h≤10" is satisfied. d indicates the depth of the recess. h indicates the height of the protruding portion.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This disclosure relates to lithium metal secondary batteries. [Background technology]

[0002] Japanese Patent Publication No. 04-004563 (Patent Document 1) discloses a negative electrode current collector having a convex shape on the side that contacts the separator. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 04-004563 [Overview of the project] [Problems that the invention aims to solve]

[0004] Lithium-metal secondary batteries (hereinafter sometimes abbreviated as "LMB (Lithium-Metal Secondary Battery)") are being investigated. The negative electrode reaction in an LMB involves the dissolution and deposition of Li. During charging, Li ions accept electrons on the surface of the negative electrode current collector, causing Li to precipitate. Li can form dendrites. It is thought that the reversibility of the negative electrode reaction decreases as the dendrites grow toward the positive electrode.

[0005] For example, it has been proposed to provide a protrusion on the negative electrode current collector. The protrusion functions as a spacer, creating a storage space around it. It is expected that the reversibility of the negative electrode reaction will be improved as Li is deposited in the storage space. However, since electrons are also supplied to the protrusion, there is a possibility that dendrites will be generated from the tip of the protrusion. In other words, Li may be deposited outside the storage space.

[0006] The purpose of this disclosure is to improve the reversibility of the negative electrode reaction. [Means for solving the problem]

[0007] The technical configuration and effects of this disclosure are described below. However, the mechanism of action includes assumptions. The mechanism of action does not limit the technical scope of this disclosure.

[0008] 1. A lithium metal secondary battery includes a power generation element and an electrolyte. The power generation element includes a positive electrode and a negative electrode. The negative electrode includes a substrate and a protrusion. The substrate is conductive. The protrusion is insulating. A recess is formed on the surface of the substrate. The protrusion is located on the surface of the substrate. The protrusion projects outward from the surface of the substrate. The relationship in the following equation is satisfied. 0.001 ≤ d / h ≤ 10 d indicates the depth of the recess, and h indicates the height of the protrusion. The depth and height are measured relative to the surface of the substrate.

[0009] In the LMB described in "1" above, the protrusions are insulating. It is assumed that electrons are not supplied to the protrusions. Li is expected to precipitate from the surface of the conductive substrate. Recesses are formed on the surface of the substrate. It is expected that the large surface area of ​​the substrate will promote the precipitation of Li from the substrate surface. Furthermore, when the depth of the recesses and the height of the protrusions satisfy a specific relationship, it is expected that the precipitation and dissolution reactions of Li in the storage space will be promoted. It is expected that the reversibility of the negative electrode reaction will be improved through the synergistic effect of these actions.

[0010] 2. The LMB described in "1" above may include, for example, the following configuration: The substrate is porous.

[0011] The porous nature of the substrate is expected to improve the uniformity of the negative electrode reaction in the in-plane direction. The substrate may also include a three-dimensional network structure. The three-dimensional interconnection of pores may improve the uniformity of the negative electrode reaction.

[0012] 3. The LMB described in "1" or "2" above may include, for example, the following configuration: A seed material is placed inside the recess. The seed material includes at least one selected from the group consisting of Li, Mg, Al, Zn, Ag, Pt, and Au.

[0013] The seed material is expected to act as a seed for Li nucleation. The seed material may be, for example, Li. The seed material may also be, for example, a metal that can alloy with Li. It is expected that the reversibility of the negative electrode reaction will be improved by placing the seed material in the recess.

[0014] 4. The LMB described in any one of items "1" to "3" above may include, for example, the following configuration: At least one selected from the group consisting of solid electrolytes and gel electrolytes is disposed inside the recess.

[0015] By placing at least one of a solid electrolyte and a gel electrolyte within the recess, it is expected that the distribution of Li ions on the surface of the substrate will become more uniform. This is expected to improve the reversibility of the negative electrode reaction.

[0016] 5. The LMB described in any one of items "1" to "4" above may include, for example, the following configuration: In a plan view, the convex portion extends linearly.

[0017] The protrusion may be, for example, wall-shaped.

[0018] 6. The LMB described in any one of items "1" to "4" above may include, for example, the following configuration: In a plan view, the convex portions are distributed in a point-like manner.

[0019] The protrusion may be, for example, columnar.

[0020] 7. The LMB described in any one of items "1" to "6" above may include, for example, the following configuration: In cross-sectional view, the convex portion has a tapered shape or an inverse tapered shape.

[0021] The tapered or inversely tapered shape of the convex portion is expected to improve the reversibility of the negative electrode reaction.

[0022] 8. The LMB described in "7" above may include, for example, the following configuration: The power generation element is a wound electrode body. The base material has an inner surface and an outer surface. In the wound electrode body, the inner surface is located on the inner side. The outer surface is the surface opposite the inner surface. A convex portion is located on each of the inner and outer surfaces. On the inner surface, the convex portion has a tapered shape. On the outer surface, the convex portion has an inverse tapered shape.

[0023] When the power generation element is a wound electrode body, for example, a large difference in reactivity between the inner and outer surfaces of the negative electrode can accelerate performance degradation. If the shape of the protrusions differs between the inner and outer surfaces, for example, the difference in reactivity between the inner and outer surfaces can be mitigated.

[0024] 9. The LMB described in "7" above may include, for example, the following configuration: The power generation element is a wound electrode body. The base material has an inner surface and an outer surface. In the wound electrode body, the inner surface is located on the inner side. The outer surface is the surface opposite the inner surface. A convex portion is located on each of the inner and outer surfaces. On the inner surface, the convex portion has an inverse tapered shape. On the outer surface, the convex portion has a tapered shape.

[0025] Even in the reverse configuration of "8" above, the difference in reactivity between the inner and outer surfaces may be mitigated.

[0026] Embodiments of the present disclosure (which may be abbreviated as "Embodiments") are described below. However, these embodiments do not limit the technical scope of the present disclosure. These embodiments are illustrative in all respects. These embodiments are non-restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from these embodiments and combined in any way. [Brief explanation of the drawing]

[0027] [Figure 1] This is a conceptual diagram showing an example of an LMB in this embodiment. [Figure 2] This is a schematic cross-sectional view showing an example of a negative electrode in this embodiment. [Figure 3] This is a schematic plan view showing the first example of a planar pattern of the convex portion. [Figure 4] This is a schematic plan view showing a second example of the planar pattern of the convex portion. [Figure 5] This is a schematic cross-sectional view showing an example of a protrusion. [Figure 6] This is a schematic cross-sectional view showing a first example of the arrangement of protrusions in a wound electrode body. [Figure 7] This is a schematic cross-sectional view showing a second example of the arrangement of protrusions in a wound electrode body. [Modes for carrying out the invention]

[0028] 1. Explanation of Terms The terms “equipped with,” “included,” “possess,” and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the essential elements. The statement “consists of” is a closed term. However, even a configuration expressed in closed terms may include additional elements that are usually incidental or irrelevant to the disclosed technology. The statement “substantially consists of…” is a semi-closed term. Semi-closed terms allow for the addition of elements that do not substantially affect the fundamental and novel characteristics of the disclosed technology.

[0029] Expressions such as "may do" and "may be" are used in a permissive sense, meaning "there is a possibility," rather than in an obligatory sense, meaning "it must be done."

[0030] Elements expressed in the singular form include plural forms unless otherwise specified. For example, "convex part" includes not only "one convex part" but also "multiple convex parts." The same applies to "concave part."

[0031] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For example, "parallel" may deviate slightly from its strict meaning. Geometric terms may include tolerances and errors in design, operation, and manufacturing. Dimensional relationships in each diagram may not match actual dimensions. Dimensional relationships in each diagram may be altered to aid the reader's understanding. For example, length, width, and thickness may be changed. Furthermore, some components may be omitted.

[0032] Numerical ranges such as "m to n%" include upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less". "m% or more and n% or less" includes "greater than m% and less than n%". "Greater than or equal to" and "less than or equal to" are represented by the equals sign inequality "≦". "Greater than" and "less than" are represented by the equals sign inequality "<". A number arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a number within the numerical range with a number listed in another part of this specification, in a table, in a figure, etc.

[0033] All numerical values ​​are modified by the term "approximately." The term "approximately" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that vary depending on how the disclosed technology is used. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, measured values ​​may be the average of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. Generally, the reliability of the average value is expected to improve with a larger number of measurements. Measured values ​​may be rounded to the nearest significant figure. Measured values ​​may include errors such as those associated with the detection limit of the measuring device.

[0034] Unless otherwise specified, the specific examples of measuring devices, etc., are merely examples. Equivalent items may be used.

[0035] The stoichiometric compositional formula shows a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to compounds with a molar ratio of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" refers to a compound containing Al and O in any compositional ratio. For example, the compound may be doped with trace elements. Some of the Al and O may be substituted with other elements.

[0036] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of substituents, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring. Derivatives of polymer compounds (resin materials) may also be called "modified products."

[0037] The term "copolymer" includes at least one selected from the group consisting of unspecified type, statistical type, random type, alternating type, periodic type, block type, and graft type.

[0038] "Plan view" refers to viewing an object (e.g., a negative electrode) from a line of sight parallel to its thickness. A plan view corresponds to a plan drawing. "Cross-sectional view" refers to viewing an object from a line of sight perpendicular to its thickness. A cross-sectional view corresponds to a cross-sectional drawing.

[0039] The "height of the protrusions" and the "depth of the recesses" are measured in a cross-sectional image of the negative electrode. The cross-section is parallel to the thickness direction. The cross-sectional image may be, for example, an optical microscope image. The cross-sectional image may also be, for example, a Scanning Electron Microscope (SEM) image. In the cross-sectional image, the surface of the substrate is used as the reference line. The height is the distance between the highest point of the protrusion and the reference line. The depth is the distance between the lowest point of the recess and the reference line. If there are multiple protrusions, the arithmetic mean is used. If there are 10 or more protrusions, the arithmetic mean of 10 randomly selected protrusions is considered the height of the protrusions. The same applies to the depth of the recesses. If the substrate is porous, open pores are considered recesses. In open pores, the vertical distance from the opening to the inner wall of the pore is considered the depth of the recess.

[0040] 2. Lithium metal rechargeable battery In lithium metal secondary batteries (LMBs), the negative electrode reaction includes the dissolution and deposition reactions of Li. In general lithium-ion secondary batteries, the deposition reaction of Li is an unintended reaction. LMBs can take any form. For example, an LMB may be cylindrical, prismatic, or laminated. The laminated type includes a metal foil laminate film as its outer casing. In this embodiment, a cylindrical LMB is described as an example.

[0041] Figure 1 is a conceptual diagram showing an example of an LMB in this embodiment. The LMB100 includes a power generation element 50 and an electrolyte (not shown). The LMB100 may further include an outer casing 90. The outer casing 90 may house the power generation element 50 and the electrolyte. The outer casing 90 may be, for example, a cylindrical metal case.

[0042] 3. Power generation elements The power generation element 50 may have any form. The power generation element 50 may include, for example, a wound electrode body or a laminated electrode body. A wound electrode body may be formed by winding a strip electrode in a spiral shape. A wound electrode body may have, for example, a cylindrical outer shape. A wound electrode body may be formed in a flat shape. A laminated electrode body may be formed by stacking electrodes in the thickness direction. A laminated electrode body may have, for example, a plate-like outer shape.

[0043] The power generation element 50 includes a positive electrode 10 and a negative electrode 20. The power generation element 50 may further include a separator 30. The separator 30 may be placed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may all be in sheet form.

[0044] 4.Negative electrode Figure 2 is a schematic cross-sectional view showing an example of a negative electrode in this embodiment. The negative electrode 20 includes a base material 21 and a protrusion 22.

[0045] 4-1. Base material The base material 21 may be, for example, in the form of a sheet. The base material 21 may be, for example, in the form of a strip. The base material 21 may have a thickness of, for example, 5 to 500 μm. The base material 21 is conductive. The base material 21 can function as a negative electrode current collector. The base material 21 may contain, for example, a metal foil. The base material 21 may contain, for example, at least one selected from the group consisting of Cu, Ni, Fe, Zn, Pb, Ag, and Au. The base material 21 may contain, for example, a Cu foil, a Cu alloy foil, etc. The base material 21 may be, for example, porous. The base material 21 may be porous as a whole or partially porous. For example, the surface of the base material 21 may be porous. The base material 21 may have, for example, a three-dimensional network structure. The base material 21 may contain, for example, a porous metal body, a nonwoven metal fabric, a powder laminated foil, etc. Powder laminated foil can be formed by sintering a metal foil and a metal powder. Powder laminated foil includes a foil portion and a powder portion. The powder portion is laminated on the surface of the foil portion. The powder portion is a sintered body. The powder portion is porous.

[0046] 4-1-1. Recess Recesses 1 are formed on the surface of the substrate 21. The recesses 1 may be formed over the entire surface of the substrate 21. The recesses 1 may be formed on only a part of the substrate 21. The number density of recesses 1 may be higher than the number density of protrusions 22. "Number density" refers to the number per unit area. For example, if the substrate 21 is a metal foil, the recesses 1 may be formed by, for example, shot peening, roughening plating, laser processing, etching, etc. For example, in laser processing, porous foil (for example, powder laminated foil, etc.) may be used. For example, conductive particles may be coated on the surface of the metal foil. Gaps between particles can form recesses 1. The conductive particles may include, for example, carbon particles, metal particles, etc. The metal particles may include, for example, the seed material described later. For example, the recesses 1 may be formed by laminating a porous metal body onto the metal foil.

[0047] In cross-sectional view, the recess 1 has a depth (d). In plan view, the recess 1 may be distributed in a point-like manner, for example. That is, the recess 1 may form a pit. In plan view, the recess 1 may extend in a linear manner, for example. That is, the recess 1 may form a trench. The recess 1 can be evaluated, for example, by the arithmetic mean height (Sa) of the surface of the substrate 21. The Sa of the substrate 21 may be, for example, 0.1 μm or more, 1 μm or more, or 5 μm or more. The Sa of the substrate 21 may be, for example, 20 μm or less, 10 μm or less, 5 μm or less, or 1 μm or less. Sa can be measured by a surface roughness meter.

[0048] The depth (d) of recess 1 may be, for example, 0.1 μm or more, 0.3 μm or more, 0.5 μm or more, 0.7 μm or more, or 0.9 μm or more. The depth (d) of recess 1 may be, for example, 1.0 μm or less, 0.9 μm or less, 0.7 μm or less, 0.5 μm or less, or 0.3 μm or less.

[0049] 4-1-2. Filling material The recess 1 may have any cross-sectional shape. The cross-sectional shape of the recess 1 may be, for example, rectangular, V-shaped, U-shaped, etc. If the base material 21 is porous, the recess 1 may have a more complex cross-sectional shape. A filler 2 may be placed inside the recess 1. The filler 2 may, for example, cover the inner wall of the recess 1. The filler 2 may fill at least a portion of the recess 1. The filling rate of the recess 1 may be, for example, 1% or more, 10% or more, 30% or more, or 50% or more. The filling rate of the recess 1 may be, for example, 100% or less, 90% or less, or 70% or less. "Filling rate" refers to the percentage of the area of ​​the filler 2 relative to the area of ​​the recess 1 in the cross-sectional image of the recess 1.

[0050] The filler 2 may contain any components. For example, the filler 2 may contain at least one selected from the group consisting of seed material, solid electrolyte, and gel electrolyte. For example, the seed material may contain at least one selected from the group consisting of Li, Mg, Al, Zn, Ag, Pt, and Au. The seed material may be in the form of a film, for example. The seed material may cover the inner wall of the recess 1, for example. The seed material may be in the form of parts, for example. The seed material may contain, for example, metal nanoparticles. The seed material may have a D50 of, for example, 1 nm to 20 nm.

[0051] The solid electrolyte may include, for example, at least one selected from the group consisting of sulfide solid electrolytes, oxide solid electrolytes, halide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes. Examples of sulfide solid electrolytes include LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, Li 10 GeP2S 12 Li4P2S6, Li7P3S 11 It may also contain at least one selected from the group consisting of Li3PS4, Li7PS6, and Li6PS5X (X = Cl, Br, I). For example, "LiI-LiBr-Li3PS4" refers to a material synthesized by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, solid electrolytes may be synthesized by a mechanochemical method. "Li2S-P2S5" contains Li3PS4. Li3PS4 can be produced, for example, by mixing Li2S and P2S5 in a molar ratio of "Li2S / P2S5 = 75 / 25".

[0052] A halide solid electrolyte may be represented by, for example, the following formula. Li 6-na M a X6 In the above formula, n represents the oxidation number of M. M may contain, for example, an atom having an oxidation number of +3. M may contain, for example, an atom having an oxidation number of +4. M may contain at least one selected from the group consisting of, for example, Y, Al, Ti, Zr, Ca, and Mg. a may satisfy the relationship 0 < a < 2. X may contain at least one selected from the group consisting of, for example, F, Cl, Br, and I.

[0053] The halide solid electrolyte may be represented, for example, by the following formula. Li 3-a Ti a Al 1-a F6 In the above formula, a may satisfy the relationship 0 ≦ a ≦ 0.1, 0.1 ≦ a ≦ 0.2, 0.2 ≦ a ≦ 0.3, 0.3 ≦ a ≦ 0.4, 0.4 ≦ a ≦ 0.5, 0.5 ≦ a ≦ 0.6, 0.6 ≦ a ≦ 0.7, 0.7 ≦ a ≦ 0.8, 0.8 ≦ a ≦ 0.9, or 0.9 ≦ a ≦ 1.

[0054] The halide solid electrolyte may be represented, for example, by the following formula. Li3YCl a Br b I 6-a-b In the above formula, the relationship 0 ≦ a + b ≦ 6 is satisfied. a may satisfy the relationship 0 ≦ a ≦ 1, 1 ≦ a ≦ 2, 2 ≦ a ≦ 3, 3 ≦ a ≦ 4, 4 ≦ a ≦ 5, or 5 ≦ a ≦ 6. b may satisfy the relationship 0 ≦ b ≦ 1, 1 ≦ b ≦ 2, 2 ≦ b ≦ 3, 3 ≦ b ≦ 4, 4 ≦ b ≦ 5, or 5 ≦ b ≦ 6.

[0055] The oxide solid electrolyte is, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3, and Li7La3Zr2O 12It may contain at least one selected from the group consisting of the following. The hydride solid electrolyte may include, for example, LiBH4. The nitride solid electrolyte may include, for example, Li3N, Li3BN2, etc.

[0056] The gel electrolyte may contain a liquid electrolyte and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polyacrylonitrile (PAN), polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0057] 4-2. Convex part The protrusions 22 are located on the surface of the base material 21. The protrusions 22 may be located on the recesses 1. The protrusions 22 may be located on only one side of the base material 21. The protrusions 22 may be located on both sides of the base material 21. The protrusions 22 are located on the surface of the base material 21 at intervals. The protrusions 22 protrude outward from the surface of the base material 21. The ratio (d / h) of the depth (d) of the recess 1 to the height (h) of the protrusions 22 is 0.001 or more and 10 or less. The ratio (d / h) may be, for example, 0.005 or more, 0.01 or more, 0.05 or more, 0.1 or more, 0.5 or more, 1 or more, or 5 or more. The ratio (d / h) may be, for example, 5 or less, 1 or less, 0.5 or less, 0.1 or less, 0.05 or less, 0.01 or less, or 0.005 or less.

[0058] The height (h) of the protrusion 22 may be, for example, greater than the depth (d) of the recess 1. The height (h) of the protrusion 22 may be, for example, smaller than the depth (d) of the recess 1. The height (h) of the protrusion 22 may be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, 30 μm or more, 50 μm or more, 70 μm or more, or 90 μm or more. The height (h) of the protrusion 22 may be, for example, 100 μm or less, 90 μm or less, 70 μm or less, 50 μm or less, 30 μm or less, 10 μm or less, or 1 μm or less.

[0059] The protrusion 22 is insulating. The volume resistivity of the protrusion 22 is, for example, 1 × 10⁻⁶ 5 Ω cm or more, 1×10 10 Ω·cm or greater, or 1 × 10⁻⁶ 15 Any value greater than or equal to Ω·cm is acceptable.

[0060] The protrusion 22 may include, for example, a ceramic material, a glass material, a resin material, etc. The protrusion 22 may include, for example, at least one selected from the group consisting of SiO2, GeO2, B2O3, P2O5, As2O5, Li2O, Na2O, K2O, MgO, CaO, BaO, Al2O3, TiO2, ZrO2, polyethylene (PE), polypropylene (PP), PVdF, polytetrafluoroethylene (PTFE), polyimide (PI), polyamide (PA), and polyamideimide (PAI).

[0061] The protrusions 22 can be formed by any method. For example, the protrusions 22 may be formed by roll-to-roll transfer. For example, the protrusions 22 may be formed by screen printing. Furthermore, the protrusions 22 may be formed by photolithography, CVD (Chemical Vapor Deposition), ALD (Atomic Layer Deposition), PVD (Physical Vapor Deposition), EPD (Electrophoretic Deposition), selective dry etching, laser processing, additive manufacturing, etc.

[0062] Figure 3 is a schematic plan view showing a first example of the planar pattern of the convex portion. The convex portion 22 may be, for example, wall-shaped. In plan view, the convex portion 22 may extend linearly, for example. The convex portion 22 may extend in a straight line, for example. The convex portion 22 may extend in a curved shape, for example. Storage spaces for Li may be formed between the convex portions 22. The planar pattern of the convex portion 22 may be, for example, a collection of parallel lines. The planar pattern of the convex portion 22 may be, for example, a grid. When the convex portion 22 is wall-shaped, the thickness of the convex portion 22 may be, for example, 1 to 1000 μm, 10 to 500 μm, 50 to 500 μm, or 100 to 500 μm. The spacing between adjacent convex portions 22 may be, for example, 1 to 1000 μm, 5 to 500 μm, 10 to 300 μm, or 50 to 500 μm.

[0063] Figure 4 is a schematic plan view showing a second example of the planar pattern of the protrusions. The protrusions 22 may be, for example, columnar. In a plan view, the protrusions 22 may be distributed, for example, as points. A storage space for Li may be formed around each protrusion 22. In a plan view, the storage space may be network-like. For example, in a plan view, the network structure of the precipitated Li may improve the reversibility of the negative electrode reaction. The arrangement of the protrusions 22 is arbitrary. The arrangement of the protrusions 22 may be random. The arrangement of the protrusions 22 may be regular. The arrangement of the protrusions 22 may be, for example, a triangular lattice, an isosceles triangular lattice, a regular triangular lattice, a rectangular lattice, a square lattice, etc. When the protrusions 22 are columnar, the diameter of the protrusions 22 may be, for example, 1 to 1000 μm, 10 to 500 μm, 50 to 500 μm, or 100 to 500 μm. The protrusions 22 may be cylindrical, angular, or the like. If the protrusions 22 are not cylindrical, the diameter of the protrusions 22 indicates the maximum diameter. The spacing between adjacent protrusions 22 may be, for example, 1 to 1000 μm, 5 to 500 μm, 10 to 300 μm, or 50 to 500 μm. The top of the protrusions 22 may be a flat surface or a curved surface. The negative electrode 20 may include both wall-shaped protrusions 22 and columnar protrusions 22.

[0064] 4-2-1. Tapered shape Figure 5 is a schematic cross-sectional view showing an example of a protrusion. The protrusion 22 may have, for example, a tapered shape or an inverse tapered shape. A "tapered shape" refers to a shape in which the protrusion 22 becomes thinner as it moves away from the base material 21. An "inverse tapered shape" refers to a shape in which the protrusion 22 becomes thicker as it moves away from the base material 21. The protrusion 22 may have a tapered shape on both sides of the base material 21. The protrusion 22 may have an inverse tapered shape on both sides of the base material 21.

[0065] The entire protrusion 22 may have a tapered shape. A part of the protrusion 22 may have a tapered shape. The tapered shape or inverse tapered shape may have any taper ratio. The taper ratio may be, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.5 or more, or 1 or more. The taper ratio may be, for example, 5 or less, 3 or less, 2 or less, or 1 or less. The taper ratio can be determined by the following formula. r=(ab) / c r: Taper ratio a: Maximum diameter of the tapered section b: Minimum diameter of the tapered section c: Distance between a and b Furthermore, when the entire protrusion 22 has a tapered shape, c may be equal to the height (h) of the protrusion 22.

[0066] Figure 6 is a schematic cross-sectional view showing a first example of the arrangement of protrusions in a wound electrode body. Figure 6 shows a cross-section perpendicular to the winding axis of the wound electrode body. In the wound electrode body, the base material 21 has an inner circumferential surface 21a and an outer circumferential surface 21b. The inner circumferential surface 21a is located on the inner circumferential side. The inner circumferential surface 21a faces the winding axis (center). The outer circumferential surface 21b is the opposite surface of the inner circumferential surface 21a. Protrusions 22 are arranged on each of the inner circumferential surface 21a and the outer circumferential surface 21b. For example, on the inner circumferential surface 21a, the protrusions 22 may have a tapered shape. For example, on the outer circumferential surface 21b, the protrusions 22 may have an inverse tapered shape. On at least one of the inner circumferential surface 21a and the outer circumferential surface 21b, the inclination of the tapered shape may be parallel to a straight line passing through the center of the wound electrode body. The angle between the tapered shape and the straight line may be, for example, 30 degrees or less, 15 degrees or less, 10 degrees or less, 5 degrees or less, or 1 degree or less.

[0067] Figure 7 is a schematic cross-sectional view showing a second example of the arrangement of protrusions in a wound electrode body. For example, the protrusion 22 may have an inverse tapered shape on the inner circumferential surface 21a. For example, the protrusion 22 may have a tapered shape on the outer circumferential surface 21b.

[0068] 5.Positive electrode The positive electrode 10 may be, for example, in the form of a sheet. The positive electrode 10 may include, for example, a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is conductive. The positive electrode current collector supports the positive electrode active material layer. The positive electrode current collector may be, for example, in the form of a sheet. The positive electrode current collector may have a thickness of, for example, 5 to 50 μm. The positive electrode current collector may include, for example, a metal foil. The positive electrode current collector may include, for example, at least one selected from the group consisting of Al, Mn, Ti, Fe, and Cr. The positive electrode current collector may include, for example, Al foil, Al alloy foil, Ti foil, stainless steel foil, etc.

[0069] An intermediate layer (not shown) may be placed between the positive electrode current collector and the positive electrode active material layer. The intermediate layer does not contain positive electrode active material. The intermediate layer may have a thickness of, for example, 0.1 to 5 μm. The intermediate layer may contain, for example, a conductive material, an insulating material, a binder, etc. The insulating material may contain, for example, alumina, boehmite, aluminum hydroxide, etc.

[0070] The positive electrode active material layer is located on the surface of the positive electrode current collector. The positive electrode active material layer may be located on only one side of the positive electrode current collector. The positive electrode active material layer may be located on both sides of the positive electrode current collector. The positive electrode active material layer may have a thickness of, for example, 10 to 1000 μm, 50 to 500 μm, or 100 to 300 μm. The positive electrode active material layer contains positive electrode active material. The positive electrode active material layer may further contain, for example, a conductive material and a binder.

[0071] 5-1. Conductive materials The conductive material can form electron conduction paths within the positive electrode active material layer. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The conductive material may contain any components. For example, the conductive material may contain at least one selected from the group consisting of graphite, acetylene black (AB), Ketjenblack (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0072] 5-2. Binder The binder can fix the positive electrode active material layer to the positive electrode current collector. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The binder may contain any components. For example, the binder may contain at least one selected from the group consisting of PVdF, PVdF-HFP, PTFE, carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0073] 5-3. Other Components The positive electrode active material layer may further contain, for example, an inorganic filler, an organic filler, a solid electrolyte, a surface modifier, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The positive electrode active material layer may contain, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, a silane coupling agent, MoS2, WO3, etc.

[0074] 5-4. Positive Electrode Active Material The positive electrode active material may be, for example, in particulate form. The positive electrode active material may contain any component. The positive electrode active material may contain, for example, a transition metal oxide, a polyanion compound, etc. Within one particle (positive electrode active material), the composition may be uniform or non-uniform. For example, the composition may be inclined from the surface to the center of the particle. The composition may change continuously or discontinuously (stepwise).

[0075] 5-4-1. Transition Metal Oxide (Space Group R-3m) The transition metal oxide may have any crystal structure. The transition metal oxide may contain, for example, a crystal structure belonging to the space group R-3m. For example, a compound represented by the general formula "LiMO2" may have a crystal structure belonging to the space group R-3m. The transition metal oxide may be represented, for example, by the following formula. Li 1-a Ni x M 1-x O2 In the above formula, the relationship of -0.5 ≦ a ≦ 0.5 and 0 < x ≦ 1 is satisfied. M may contain, for example, at least one selected from the group consisting of Co, Mn, and Al.

[0076] In the above formula, x may satisfy a relationship such as 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x ≤ 1. a may satisfy a relationship such as -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1.

[0077] The transition metal oxide may include, for example, at least one selected from the group consisting of LiCoO2, LiMnO2, LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and LiNiO2.

[0078] 5-4-1-1.NCM The transition metal oxide may be represented, for example, by the following formula. The compound represented by the following formula may also be referred to as "NCM". Li 1-a Ni x Co y Mn z O2 In the above formula, the relationships -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied.

[0079] In the above formula, x may satisfy a relationship such as 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1.

[0080] In the above formula, y may satisfy a relationship such as 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1.

[0081] In the above formula, z may satisfy a relationship such as 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1.

[0082] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and LiNi 0.9 Co 0.05 Mn 0.05 may contain at least one selected from the group consisting of O2.

[0083] 5-4-1-2.NCA The transition metal oxide may be represented, for example, by the following formula. The compound represented by the following formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the above formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied.

[0084] In the above formula, x may satisfy, for example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1.

[0085] In the above formula, y may satisfy, for example, the relationship of 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1.

[0086] In the above formula, z may satisfy, for example, the relationship of 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦ 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1.

[0087] NCA may be, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1 Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al0.05 O2, and LiNi 0.9 Co 0.05 Al 0.05 It may contain at least one selected from the group consisting of O2.

[0088] 5-4-1-3. Multicomponent system The positive electrode active material may contain, for example, two or more types of NCM or the like. The positive electrode active material may contain, for example, NCM(0.6≦x) and NCM(x<0.6). "NCM(0.6≦x)" refers to a compound in the general formula "Li 1-a Ni x Co y Mn z O2" where x (Ni ratio) is 0.6 or more. NCM(0.6≦x) may be referred to as, for example, a "high nickel material". NCM(0.6≦x) contains, for example, LiNi 0.8 Co 0.1 Mn 0.1 O2 and the like. "NCM(x<0.6)" refers to a compound in the general formula "Li 1-a Ni x Co y Mn z O2" where x (Ni ratio) is less than 0.6. NCM(x<0.6) contains, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 and the like. The mixing ratio (mass ratio) of NCM(0.6≦x) and NCM(x<0.6) may be, for example, any of "NCM(0.6≦x) / NCM(x<0.6)=9 / 1 to 1 / 9", "NCM(0.6≦x) / NCM(x<0.6)=9 / 1 to 4 / 6", or "NCM(0.6≦x) / NCM(x<0.6)=9 / 1 to 3 / 7".

[0089] The positive electrode active material may contain, for example, both NCA and NCM. The mixing ratio (mass ratio) of NCA to NCM may be, for example, "NCA / NCM = 9 / 1 to 1 / 9", "NCA / NCM = 9 / 1 to 4 / 6", or "NCA / NCM = 9 / 1 to 3 / 7". The Ni ratio between NCA and NCM may be the same or different. The Ni ratio of NCA may be higher than that of NCM. The Ni ratio of NCA may be lower than that of NCM.

[0090] 5-4-2.Transition metal oxides (space group C2 / m) Transition metal oxides may include, for example, a crystal structure belonging to the space group C2 / m. Transition metal oxides may also be represented by, for example, the following formula. Li2MO3 In the above formula, M may include, for example, at least one selected from the group consisting of Ni, Co, Mn, and Fe.

[0091] The positive electrode active material may include, for example, a mixture of LiMO2 (space group R-3m) and Li2MO3 (space group C2 / m). The positive electrode active material may also include, for example, a solid solution of LiMO2 and Li2MO3 (Li2MO3-LiMO2).

[0092] 5-4-3.Transition metal oxides: space group Fd-3m Transition metal oxides may include, for example, crystal structures belonging to the space group Fd-3m. Transition metal oxides may also be represented by, for example, the following formula. LiMn 2-x M x O4 In the above equation, the relationship 0 ≤ x ≤ 2 is satisfied. M may include, for example, at least one selected from the group consisting of Ni, Fe, and Zn.

[0093] LiM2O4 (space group Fd-3m) is, for example, LiMn2O4 and LiMn 1.5 Ni 0.5The positive electrode active material may contain at least one selected from the group consisting of O4. The positive electrode active material may contain, for example, a mixture of LiMO2 (space group R-3m) and LiM2O4 (space group Fd-3m). The mixing ratio (mass ratio) of LiMO2 (space group R-3m) and LiM2O4 (space group Fd-3m) may be, for example, "LiMO2 / LiM2O4 = 9 / 1 to 9 / 1", "LiMO2 / LiM2O4 = 9 / 1 to 5 / 5", or "LiMO2 / LiM2O4 = 9 / 1 to 7 / 3".

[0094] 5-4-4. Polyanionic Compounds The polyanionic compound may contain, for example, phosphates (e.g., LiFePO4), silicates, borates, etc. The polyanionic compound may be represented by, for example, one of the following formulas. LiMPO4, Li 2-x MPO4F, Li2MSiO4, or LiMBO3 In the above formula, M may include at least one selected from the group consisting of Fe, Mn, and Co, for example. In the above formula, the relationship 0 ≤ x ≤ 2 may be satisfied, for example.

[0095] The positive electrode active material may, for example, contain a mixture of LiMO2 (space group R-3m) and a polyanionic compound. The mixing ratio (mass ratio) of LiMO2 (space group R-3m) and the polyanionic compound may be, for example, "LiMO2 / polyanionic compound = 9 / 1 to 9 / 1", "LiMO2 / polyanionic compound = 9 / 1 to 5 / 5", or "LiMO2 / polyanionic compound = 9 / 1 to 7 / 3".

[0096] 5-4-5. Dopant A dopant may be added to the positive electrode active material. The dopant may be diffused throughout the particle or distributed locally. For example, the dopant may be unevenly distributed on the particle surface. The dopant may be a substitutional solid solution atom or an interstitial solid solution atom. The amount of dopant added (mole fraction relative to the total positive electrode active material) may be, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%. One type of dopant may be added, or two or more types of dopants may be added. Two or more types of dopants may form a complex.

[0097] The dopant may include, for example, at least one selected from the group consisting of B, C, N, halogens, Si, Na, Mg, Al, Mn, Co, Cr, Sc, Ti, V, Cu, Zn, Ga, Ge, Se, Sr, Y, Zr, Nb, Mo, In, Pb, Bi, Sb, Sn, W, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and actinides.

[0098] For example, NCA may contain the following combinations: "Zr, Mg, W, Sm", "Ti, Mn, Nb, Si, Mo", or "Er, Mg".

[0099] For example, Ti may be added to NCM. For example, the combination of "Zr, W", the combination of "Si, W", or the combination of "Zr, W, Al, Ti, Co" may be added to NCM.

[0100] 5-4-6. Surface coating The positive electrode 10 may contain composite particles. The composite particles include core particles and a coating layer. The core particles contain positive electrode active material. The coating layer covers at least a portion of the surface of the core particles. The coating layer may have a thickness of, for example, 1 to 3000 nm, 5 to 2000 nm, 10 to 1000 nm, 10 to 100 nm, or 10 to 50 nm. The thickness of the coating layer can be measured, for example, in an SEM image of the particle cross-section. That is, the sample is prepared by embedding the composite particles in a resin material. The sample is cross-sectionalized using an ion milling device. For example, an ion milling device manufactured by Hitachi High-Technologies Corporation, "product name ArBlade(registered trademark) 5000," may be used. The cross-section of the sample is observed by SEM. For example, an SEM device manufactured by Hitachi High-Technologies Corporation, "product name SU8030," may be used. For each of the 10 composite particles, the thickness of the coating layer is measured in 20 fields of view. The arithmetic mean of the thicknesses at a total of 200 points is used.

[0101] The percentage of the core particle surface covered by the coating layer is also called the "coverage rate." The coverage rate may be, for example, 1% or more, 10% or more, 30% or more, 50% or more, or 70% or more. The coverage rate may also be, for example, 100% or less, 90% or less, or 80% or less.

[0102] Coverage can be measured, for example, by XPS (X-ray Photoelectron Spectroscopy). For example, an XPS instrument manufactured by ULVAC-PHIE, "product name PHI X-tool," may be used. A sample powder consisting of composite particles is placed in the XPS. Narrow scan analysis is performed. The measurement data is processed by analysis software. For example, analysis software manufactured by ULVAC-PHIE, "product name MulTiPak," may be used. By analyzing the measurement data, multiple elements are detected. The ratio of each detected element is determined from the area of ​​each peak. Coverage is calculated using the following formula. θ = {I1 / (I0+I1)} × 100 θ: Coverage rate [%] I0: Ratio of elements derived from core particles I1: Ratio of elements derived from the coating layer For example, if the core particles contain NCM, I0 represents the total elemental ratio of "Ni, Co, Mn". For example, if the core particles contain NCA, I0 represents the total elemental ratio of "Ni, Co, Al". For example, if the coating layer contains P and B, I1 represents the total elemental ratio of "P, B".

[0103] The coating layer may contain any components. For example, the coating layer may contain elements, organic substances, inorganic acid salts, organic acid salts, hydroxides, oxides, carbides, nitrides, sulfides, halides, etc. The coating layer may contain, for example, B, Al, W, Zr, Ti, Co, F, lithium compounds (e.g., Li2CO3, LiHCO3, LiOH, Li2O, etc.), tungsten oxide (e.g., WO3, etc.), titanium oxide (e.g., TiO2, etc.), zirconium oxide (e.g., ZrO2), boron oxide, boron phosphate (e.g., BPO4, etc.), aluminum oxide (e.g., Al2O3, etc.), boehmite, aluminum hydroxide, phosphates (e.g., Li3PO4, etc.). 4、 (NH4)3PO4, AlPO4, borates (e.g., Li2B4O7, LiBO3, etc.), polyacrylates (Li salt, Na salt, NH4 salt, etc.), acetates (e.g., Li salt, etc.), CMC (Na salt, Li salt, NH4 salt, etc.), LiNbO 3、 It may also contain Li2TiO3 and at least one selected from the group consisting of Li-containing halides (e.g., LiAlCl4, LiTiAlF6, LiYBr6, LiYCl6, etc.).

[0104] 5-4-7. Hollow particles / Solid particles Hollow particles are secondary particles. In a cross-sectional image of a hollow particle, the area of ​​the central cavity accounts for 30% or more of the total area of ​​the particle. The proportion of the cavity in a hollow particle may be, for example, 40% or more, 50% or more, or 60% or more. Solid particles are secondary particles. In a cross-sectional image of a solid particle, the area of ​​the central cavity accounts for less than 30% of the total area of ​​the particle. The proportion of the cavity in a solid particle may be, for example, 20% or less, 10% or less, or 5% or less. The positive electrode active material may be hollow particles or solid particles. A mixture of hollow particles and solid particles may be used. The mixing ratio (mass ratio) of hollow particles to solid particles can be any of the following, for example: "hollow particles / solid particles = 1 / 9 to 9 / 1", "hollow particles / solid particles = 2 / 8 to 8 / 2", "hollow particles / solid particles = 3 / 7 to 7 / 3", or "hollow particles / solid particles = 4 / 6 to 6 / 4".

[0105] 5-4-8. Large particles / small particles The positive electrode active material may, for example, have a unimodal particle size distribution (number-based). The positive electrode active material may, for example, have a multimodal particle size distribution. The positive electrode active material may, for example, have a bimodal particle size distribution. That is, the positive electrode active material may contain large and small particles. When the particle size distribution is bimodal, the particle size corresponding to the peak top of the larger particle size is the particle size of the large particle (d L ) is considered to be the particle size of the smallest particle (d S ) is considered to be the particle size ratio (d L / d S ) could be, for example, 2 to 10, 2 to 5, or 2 to 4. d L For example, it may be 8 to 20 μm, or 8 to 15 μm. S This can be, for example, 1 to 10 μm or 1 to 5 μm.

[0106] For example, the particle size distribution may be subjected to peak separation processing using waveform analysis software. Peak area (S) originating from large particles. L ) and the peak area (S) originating from small particles SThe ratio to ) is, for example, "S L / S S =1 / 9 to 9 / 1", S L / S S =5 / 5 to 9 / 1" or "S L / S S It can be any of the dates from 7 / 3 to 9 / 1.

[0107] The particle size distribution based on particle count is measured by microscopy. Multiple cross-sectional samples are taken from the positive electrode active material layer. The cross-sectional samples may include, for example, a cross-section perpendicular to the surface of the positive electrode active material layer. The surface to be observed is cleaned, for example, by ion milling. The cross-sectional samples are observed using a scanning electron microscope (SEM). The observation magnification is adjusted so that 10 to 100 particles fit within the observation field of view. The Ferret diameter of all particles in the image is measured. The "Ferret diameter" indicates the distance between the two furthest points on the contour line of the particle. By observing multiple cross-sectional samples, a total of 1000 or more Ferret diameters are obtained. From these 1000 or more Ferret diameters, a particle size distribution based on particle count is created.

[0108] A bimodal particle size distribution can be formed by mixing two types of particles. The two types of particles have different particle size distributions. For example, the two types of particles may have different D50s. "D50" refers to the particle size at which the cumulative frequency from the smaller particle size side reaches 50% in the volume-based particle size distribution. D50 can be measured by laser diffraction. The sample to be measured is a powder. For example, the large particles may have a D50 of 8 to 20 μm or 8 to 15 μm. For example, the small particles may have a D50 of 1 to 10 μm or 1 to 5 μm. The ratio of the D50 of the large particles to the D50 of the small particles may be, for example, 2 to 10, 2 to 5, or 2 to 4. The mixing ratio (mass ratio) of large particles to small particles can be any of the following: for example, "large particles / small particles = 1 / 9 to 9 / 1", "large particles / small particles = 5 / 5 to 9 / 1", or "large particles / small particles = 7 / 3 to 9 / 1".

[0109] The large particles and small particles may have the same composition or different compositions. For example, the large particles may be NCA and the small particles may be NCM. For example, the large particles may be NCM (0.6 ≤ x) and the small particles may be NCM (x < 0.6).

[0110] 6. Electrolytes The electrolyte contains dissolved Li. The electrolyte may be either a liquid electrolyte or a gel electrolyte. A liquid electrolyte may, for example, contain an electrolyte solution. The electrolyte solution contains a solvent and a solute.

[0111] 6-1.Solute The solute concentration may be, for example, 0.5 to 1 mol / L, 1 to 1.5 mol / L, 1.5 to 2 mol / L, 2 to 2.5 mol / L, or 2.5 to 3 mol / L. The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0112] 6-2. Solvent 6-2-1. Ether-based solvents The electrolyte may contain an ether-based solvent. The solvent may contain, for example, hydrofluoroether (HFE). The HFE may contain at least one selected from the group consisting of, for example, difluoromethyl group, 2,2-difluoroethyl group, 2,2,2-trifluoroethyl group, 1,1,2,2-tetrafluoroethyl group, 2,2,3,3,3-pentafluoropropyl group, 2,2,3,3-tetrafluoropropyl group, 1,1,1,3,3,3-hexafluoroisopropyl group, 1,1,2,3,3,3-hexafluoropropyl group, 2,2,3,3,4,4,4-heptafluorobutyl group, 2,2,3,3,4,4-hexafluorobutyl group, and 2,2,3,3,4,4,5,5-octafluoropentyl group.

[0113] HFE may include, for example, at least one selected from the group consisting of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), 2,2,2-trifluoroethyl ether, difluoromethyl 2,2,3,3-tetrafluoropropyl ether, 2,2,3,3-tetrafluoropropyl 1,1,2,3,3,3-hexafluoropropyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl 1,1,2,2-tetrafluoroethyl ether, and derivatives thereof.

[0114] The solvent may also contain ethers other than HFE (hereinafter also referred to as "secondary ethers"). The secondary ether may include, for example, at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), ethylglycylm, triglycylm, tetraglycylm, and derivatives thereof. The solvent may, for example, contain 1 to 50% by volume of secondary ether (such as DME) and the remainder as HFE. The solvent may, for example, contain 10 to 40% by volume of secondary ether and the remainder as HFE.

[0115] 6-2-2. Carbonate-based solvents The electrolyte may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, cyclic carbonates, linear carbonates, fluorinated carbonates, etc. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0116] The solvent may contain cyclic carbonates (EC, PC, FEC, etc.) and linear carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to linear carbonates may be, for example, "cyclic carbonate / linear carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / linear carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / linear carbonate = 3 / 7 to 4 / 6".

[0117] The solvent may contain cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to fluorinated cyclic carbonates may be any of the following, for example: "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1 to 90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3", or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9".

[0118] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy, for example, the relationship shown in the following formula. V EC +V FEC +V EMC +V DMC +V DEC =10 In the above formula, V EC , V FEC , V EMC , V DMC , V DEC These represent the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively. 1 ≤ V EC ≤4, 0 ≤V FEC ≤3,V EC +V FEC ≤4, 0≦V EMC ≤9, 0 ≤V DMC ≤9, 0 ≤V DEC ≤9,6≦V EMC +V DMC +V DEC ≤9 The relationship is satisfied.

[0119] In the above formula, For example, 1 ≤ V EC ≤ 2, or 2 ≤ V EC The condition ≤ 3 may also be satisfied. For example, 1 ≤ V FEC ≤ 2, or 2 ≤ V FEC The condition ≤ 4 may also be satisfied. For example, 3 ≤ V EMC ≤4, or 6 ≤V EMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DMC ≤4, or 6 ≤V DMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DEC ≤4, or 6 ≤V DEC The condition ≤ 8 may also be satisfied.

[0120] The solvent may have compositions such as "EC / EMC=3 / 7", "EC / DMC=3 / 7", "EC / FEC / DEC=1 / 2 / 7", "EC / DMC / EMC=3 / 4 / 3", "EC / DMC / EMC=3 / 3 / 4", "EC / FEC / DMC / EMC=2 / 1 / 4 / 3", "EC / FEC / DMC / EMC=1 / 2 / 4 / 3", "EC / FEC / DMC / EMC=2 / 1 / 3 / 4", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4" in volume ratio.

[0121] 6-3. Additives The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additives may include, for example, gas generating agents, overcharge prevention agents, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0122] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), propanesultone (PS), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters [e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.], fluorobenzenes [e.g., monofluorobenzene (FB), 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluene (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorides (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylenes (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methyl benzothiazole) It may contain at least one selected from the group consisting of nzothiazole, tetrathiafluban, etc., nitrile compounds (e.g., adiponitrile, succinonitrile, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and derivatives thereof.

[0123] The components mentioned above may be used as solutes and solvents, or as trace components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0124] 6-4. Ionic Liquids The liquid electrolyte may include an ionic liquid. The liquid electrolyte may include, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0125] 6-5. Gel Electrolytes The gel electrolyte may contain a liquid electrolyte and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, PAN, PVdF-PAN, PEO, PEG, and derivatives thereof.

[0126] 7. Separator The separator 30 can separate the positive electrode 10 from the negative electrode 20. The separator 30 is electrically insulating. The separator 30 may include at least one selected from the group consisting of, for example, a resin film, an inorganic particle layer, and an organic particle layer. For example, the separator 30 may include a resin film and an inorganic particle layer.

[0127] 7-1. Resin film The resin film is porous. The resin film may include, for example, a microporous membrane, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a mesh-like manner. Pores are formed in the gaps of the resin skeleton. The resin film can permeate electrolytes. The resin film may have, for example, an average pore diameter of 1 μm or less. The resin film may have, for example, an average pore diameter of 0.01 to 1 μm, or 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The resin film is subjected to, for example, 50 to 250 s / 100 cm. 3 It may have a Gaulle value. The "Garle value" can be measured by the Gaulle test method.

[0128] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, PE, PP, PA, PAI, PI, aromatic polyamides (aramids), polyphenylene ethers (PPE), and derivatives thereof. The resin film can be formed by, for example, a stretching method or a phase separation method. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0129] The resin film may have, for example, a single-layer structure. The resin film may consist of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multilayer structure. The resin film may include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin film may have, for example, a three-layer structure. The resin film may be formed by laminating a PP layer, a PE layer and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0130] 7-2.Inorganic particle layer The inorganic particle layer may be formed on the surface of the resin film. The inorganic particle layer may be formed on only one side of the resin film, or on both sides. The inorganic particle layer may be formed on the surface facing the positive electrode 10, or on the surface facing the negative electrode 20. Furthermore, the inorganic particle layer may be formed on the surface of the positive electrode 10.

[0131] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be called "inorganic fillers". Pores are formed in the gaps between the inorganic particles. The inorganic particle layer may have a thickness of, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called an "HRL (Heat Resistance Layer)". The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The inorganic particles may have a D50 of, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0132] 7-3.Organic particle layer The separator 30 may, for example, include an organic particle layer. The separator 30 may, for example, include an organic particle layer instead of a resin film. The separator 30 may, for example, include an organic particle layer instead of an inorganic particle layer. The separator 30 may include both a resin film and an organic particle layer. The separator 30 may include both an inorganic particle layer and an organic particle layer. The separator 30 may include all of the resin film, inorganic particle layer, and organic particle layer.

[0133] The organic particle layer may have a thickness of, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer contains organic particles. The organic particles may also be called "organic fillers". The organic particles may contain heat-resistant materials. The organic particles may contain at least one selected from the group consisting of, for example, PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The organic particles may have a D50 of, for example, 0.1 to 10 μm or 0.5 to 3 μm.

[0134] The separator 30 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles. [Explanation of symbols]

[0135] 1 recess, 2 filler, 10 positive electrode, 20 negative electrode, 21 base material, 21a inner surface, 21b outer surface, 22 protrusion, 30 separator, 50 power generation element, 51 straight line, 90 casing, 100 lithium metal secondary battery (LMB).

Claims

1. It includes a power generation element and an electrolyte, The aforementioned power generation element includes a positive electrode and a negative electrode. The negative electrode includes a base material and a protrusion, The aforementioned substrate is conductive, The aforementioned protrusion is insulating, A recess is formed on the surface of the substrate, The aforementioned protrusion is arranged on the surface of the substrate, The aforementioned protrusions protrude outward from the surface of the substrate, formula: 0.001 ≤ d / h ≤ 10 The relationship is satisfied, In the above formula, d indicates the depth of the recess, h indicates the height of the protrusion, and The depth and height are determined with respect to the surface of the substrate. At the bottom of the recess, the thickness of the substrate is reduced by the depth of the recess. A gel electrolyte is placed inside the recess. Lithium metal rechargeable battery.

2. The substrate is porous. The lithium metal secondary battery according to claim 1.

3. A seed material is placed inside the recess, and The seed material includes at least one selected from the group consisting of Mg, Al, Zn, Ag, Pt, and Au. The lithium metal secondary battery according to claim 1.

4. In a plan view, the convex portion extends in a linear manner. The lithium metal secondary battery according to claim 1.

5. In a plan view, the convex portions are distributed in a point-like manner. The lithium metal secondary battery according to claim 1.

6. In cross-sectional view, the convex portion has a tapered shape or an inverse tapered shape. A lithium metal secondary battery according to any one of claims 1 to 5.

7. The aforementioned power generation element is a wound electrode body, The substrate has an inner surface and an outer surface, In the wound electrode body, the inner circumferential surface is positioned on the inner circumferential side. The outer circumferential surface is the surface opposite to the inner circumferential surface. The protrusions are arranged on each of the inner and outer surfaces. In the inner circumferential surface, the protrusion has the tapered shape, On the outer circumferential surface, the protrusion has the inverse tapered shape. The lithium metal secondary battery according to claim 6.

8. The aforementioned power generation element is a wound electrode body, The substrate has an inner surface and an outer surface, In the wound electrode body, the inner circumferential surface is positioned on the inner circumferential side. The outer circumferential surface is the surface opposite to the inner circumferential surface. The protrusions are arranged on each of the inner and outer surfaces. On the inner circumferential surface, the protrusion has the inverse tapered shape, On the outer circumferential surface, the protrusion has the tapered shape. The lithium metal secondary battery according to claim 6.

9. formula: 0.3 μm ≤ d ≤ 1 μm The relationship is satisfied, The lithium metal secondary battery according to claim 1.

10. formula: 0.001 ≤ d / h ≤ 0.1 The relationship is satisfied, A lithium metal secondary battery according to claim 1 or claim 9.

11. Containing a liquid electrolyte, A lithium metal secondary battery according to claim 1 or claim 9.

12. The protrusion is located on the surface of the substrate in a portion where the recess is absent. A lithium metal secondary battery according to claim 1 or claim 9.

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