Positive electrode material for electric device, and positive electrode for electric device and electric device using the same

Abstract

The purpose of the present invention is to provide a means that enables an electric device, which uses a positive electrode active material that contains sulfur, to have improved cycle durability. The present invention provides a positive electrode material for electric devices, the positive electrode material comprising, within pores of a porous conductor, composite material particles containing a positive electrode active material that contains sulfur, and an electron conductor that covers the surfaces of the composite material particles.

Description

[Technical Field]

[0001] The present invention relates to a positive electrode material for an electric device, and a positive electrode for an electric device and an electric device using the same. [Background technology]

[0002] In recent years, there has been a strong desire to reduce carbon dioxide emissions in order to combat global warming. The automotive industry is hoping that the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs) will help reduce carbon dioxide emissions, and there has been active development of non-aqueous electrolyte secondary batteries, such as secondary batteries for driving motors, which hold the key to putting these vehicles into practical use.

[0003] Secondary batteries for driving motors are required to have extremely high output characteristics and high energy compared to consumer lithium secondary batteries used in mobile phones, laptops, etc. Therefore, lithium secondary batteries, which have the highest theoretical energy of all practical batteries, have attracted attention and are currently being rapidly developed.

[0004] Currently widely used lithium secondary batteries use flammable organic electrolytes, and these liquid-based lithium secondary batteries require stricter safety measures against leakage, short circuits, overcharging, and other issues than other batteries.

[0005] Therefore, in recent years, research and development of all-solid-state lithium secondary batteries using oxide- or sulfide-based solid electrolytes has been actively pursued. Solid electrolytes are materials primarily composed of ionic conductors capable of ion conduction in a solid state. Therefore, all-solid-state lithium secondary batteries, in principle, do not encounter the various problems associated with flammable organic electrolytes that are common in conventional liquid-based lithium secondary batteries. Furthermore, the use of high-potential, high-capacity positive electrode materials and high-capacity negative electrode materials generally leads to significant improvements in the battery's power density and energy density. For example, elemental sulfur (S8) has an extremely high theoretical capacity of approximately 1670 mAh / g and is advantageously low cost and abundant in resources.

[0006] On the other hand, due to the low electronic conductivity of sulfur, the high capacity characteristic of sulfur-containing positive electrode active materials has not yet been fully utilized.

[0007] For example, Japanese Patent Application Laid-Open No. 2014-17241 discloses a method for producing thin-film sulfur-coated conductive carbon, which involves immersing conductive carbon having a predetermined specific surface area in a sulfur solution and then separating the carbon from the sulfur solution, with the aim of fully utilizing the high capacity characteristics of a positive electrode active material such as elemental sulfur. According to this document, the resulting thin-film sulfur-coated conductive carbon is prone to diffusion of electrons and lithium ions within the sulfur, and therefore, by using this as a positive electrode mixture, an all-solid-state lithium-sulfur battery with excellent discharge capacity and rate characteristics can be provided. Summary of the Invention [Problem to be solved by the invention]

[0008] However, according to the investigations of the present inventors, it has been found that when the technology described in JP 2014-17241 A is adopted as a positive electrode material for an electric device, the cycle durability of the electric device to which the positive electrode material is applied may not be sufficiently ensured.

[0009] Therefore, an object of the present invention is to provide a means for improving the cycle durability of an electric device using a positive electrode active material containing sulfur. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that the above-mentioned problems can be solved by coating the surfaces of composite particles, in which a sulfur-containing positive electrode active material is filled into the pores of a porous electric conductor, with an electron conductor, thereby completing the present invention.

[0011] One aspect of the present invention is a positive electrode material for an electric device, comprising: composite particles containing a positive electrode active material containing sulfur within the pores of a porous conductor; and an electron conductor coating the surfaces of the composite particles. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing the appearance of a flat laminated type all-solid-state lithium secondary battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line 2-2 shown in FIG. [Figure 3] FIG. 3 is a cross-sectional schematic diagram of a prior art positive electrode material. [Figure 4] FIG. 4 is a cross-sectional view of a positive electrode material according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] One aspect of the present invention is a positive electrode material for an electric device, comprising composite particles containing a sulfur-containing positive electrode active material and an electron conductor coated on the surfaces of the composite particles, the composite particles being disposed within the pores of a porous conductor. The positive electrode material for an electric device according to this aspect can improve the cycle durability of an electric device using a sulfur-containing positive electrode active material.

[0014] The following describes the above-mentioned embodiment of the present invention with reference to the drawings. However, the technical scope of the present invention should be defined based on the claims and is not limited to the following embodiments. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios. In this specification, the range "X to Y" means "X or more and Y or less." Furthermore, unless otherwise specified, operations and measurements of physical properties are performed at room temperature (20 to 25°C) and a relative humidity of 40 to 50% RH.

[0015] The present invention will be described below using as an example a stacked-type (internal parallel connection) all-solid-state lithium secondary battery, which is one type of electrical device. As described above, the solid electrolyte that constitutes an all-solid-state lithium secondary battery is a material primarily composed of an ion conductor capable of ion conduction in a solid. Therefore, all-solid-state lithium secondary batteries have the advantage that, in principle, they do not encounter the various problems associated with flammable organic electrolytes that occur in conventional liquid-based lithium secondary batteries. Furthermore, the use of high-potential, high-capacity positive electrode materials and high-capacity negative electrode materials generally has the advantage of significantly improving the output density and energy density of the battery.

[0016] FIG. 1 is a perspective view showing the appearance of a flat laminated type all-solid-state lithium secondary battery according to one embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. 1. By adopting a laminated type, the battery can be made compact and have a high capacity. In this specification, the flat laminated type non-bipolar all-solid-state lithium secondary battery shown in FIGS. 1 and 2 (hereinafter also simply referred to as a "laminated type battery") will be described in detail as an example.

[0017] 1, the stacked battery 10a has a flat, rectangular shape, with a negative electrode current collector 25 and a positive electrode current collector 27 extending from both sides for extracting power. The power generating element 21 is wrapped in the battery exterior material (laminate film 29) of the stacked battery 10a, and the periphery is heat-sealed, with the negative electrode current collector 25 and positive electrode current collector 27 extending to the outside.

[0018] As shown in FIG. 2, the stacked battery 10a of this embodiment has a structure in which a flat, approximately rectangular power generating element 21, where charge and discharge reactions actually proceed, is sealed inside a laminate film 29, which is a battery exterior material. Here, the power generating element 21 has a configuration in which a positive electrode, a solid electrolyte layer 17, and a negative electrode are laminated. The positive electrode has a structure in which positive electrode active material layers 15 containing a positive electrode active material are disposed on both sides of a positive electrode current collector 11". The negative electrode has a structure in which negative electrode active material layers 13 containing a negative electrode active material are disposed on both sides of a negative electrode current collector 11'. As a result, the adjacent positive electrode, solid electrolyte layer, and negative electrode constitute one single cell layer 19.

[0019] Negative electrode current collector 11′ and positive electrode current collector 11″ are respectively attached with negative electrode current collector (tab) 25 and positive electrode current collector (tab) 27 that are electrically connected to the respective electrodes (positive and negative electrodes), and are structured so as to be sandwiched between the ends of laminate film 29, which is the battery outer casing material, and extended to the outside of laminate film 29. Positive electrode current collector 27 and negative electrode current collector 25 may be attached to positive electrode current collector 11″ and negative electrode current collector 11′ of the respective electrodes by ultrasonic welding, resistance welding, or the like, via positive electrode leads and negative electrode leads (not shown) as necessary.

[0020] The main components of the all-solid-state lithium secondary battery according to this embodiment will be described below.

[0021] [Current collector] The current collector has a function of mediating the transfer of electrons from the electrode active material layer. The material constituting the current collector is not particularly limited, and for example, a metal or a conductive resin can be used. Note that if the negative electrode active material layer and the positive electrode active material layer described later are conductive and can exhibit a current collecting function, it is not necessary to use a current collector as a member separate from these electrode active material layers.

[0022] [Negative electrode (negative electrode active material layer)] In the stacked battery according to the embodiment shown in FIGS. 1 and 2, the negative electrode active material layer 13 contains a negative electrode active material. The type of negative electrode active material is not particularly limited, but examples include carbon materials, metal oxides, and metal active materials. Silicon-based negative electrode active materials and tin-based negative electrode active materials may also be used. Silicon and tin belong to Group 14 elements and are known to be negative electrode active materials that can significantly improve the capacity of lithium secondary batteries. These elements can absorb and release a large number of charge carriers (such as lithium ions) per unit volume (mass), resulting in high-capacity negative electrode active materials. Furthermore, a lithium-containing metal may also be used as the negative electrode active material. Such a negative electrode active material is not particularly limited as long as it is a lithium-containing active material, and examples thereof include metallic lithium and lithium-containing alloys. Examples of lithium-containing alloys include alloys of Li with at least one of In, Al, Si, and Sn. The negative electrode active material preferably includes metallic lithium or a lithium-containing alloy, a silicon-based negative electrode active material, or a tin-based negative electrode active material, and particularly preferably includes metallic lithium or a lithium-containing alloy. When metallic lithium or a lithium-containing alloy is used as the negative electrode active material, the lithium secondary battery as an electrical device may be a so-called lithium deposition type in which metallic lithium as the negative electrode active material is deposited on the negative electrode current collector during the charging process. Therefore, in this configuration, the thickness of the negative electrode active material layer increases as the charging process progresses, and the thickness of the negative electrode active material layer decreases as the discharging process progresses. The negative electrode active material layer may not be present during full discharge, but in some cases, a negative electrode active material layer consisting of a certain amount of metallic lithium may be present during full discharge.

[0023] The content of the negative electrode active material in the negative electrode active material layer is not particularly limited, but is preferably within the range of 40 to 99 mass %, and more preferably within the range of 50 to 90 mass %, for example.

[0024] The negative electrode active material layer preferably further contains a solid electrolyte. By including the solid electrolyte in the negative electrode active material layer, the ionic conductivity of the negative electrode active material layer can be improved. Examples of the solid electrolyte include sulfide solid electrolytes and oxide solid electrolytes, and the sulfide solid electrolyte is preferred.

[0025] Examples of sulfide solid electrolytes include LiI-Li2S-SiS2, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, LiI-Li3PS4, LiI-LiBr-Li3PS4, Li3PS4, Li2SP2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2OLiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2- Examples include LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-ZmSn (where m and n are positive numbers and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, and Li2S-SiS2-LixMOy (where x and y are positive numbers and M is P, Si, Ge, B, Al, Ga, or In). Note that the term "Li2S-P2S5" refers to a sulfide solid electrolyte obtained using a raw material composition containing Li2S and P2S5, and the same applies to other terms.

[0026] The sulfide solid electrolyte may have, for example, a Li3PS4 skeleton, a Li4P2S7 skeleton, or a Li4P2S6 skeleton. Examples of sulfide solid electrolytes having a Li3PS4 skeleton include LiI-Li3PS4, LiI-LiBr-Li3PS4, and Li3PS4. Examples of sulfide solid electrolytes having a Li4P2S7 skeleton include Li-PS-based solid electrolytes known as LPS (for example, Li7P3S 11 ) can be mentioned. In addition, examples of sulfide solid electrolytes include Li (4-x) Ge (1-x) P xAn LGPS or the like represented by S4 (where 0 < x < 1) may be used. Among these, the sulfide solid electrolyte contained in the active material layer is preferably a sulfide solid electrolyte containing P element, and more preferably, the sulfide solid electrolyte is a material mainly composed of Li2S - P2S5. Further, the sulfide solid electrolyte may contain a halogen (F, Cl, Br, I). In a preferred embodiment, the sulfide solid electrolyte contains Li6PS5X (where X is Cl, Br or I, preferably Cl).

[0027] The ionic conductivity (for example, Li ion conductivity) of the sulfide solid electrolyte at room temperature (25 °C) is, for example, 1 × 10 -5 S / cm or more, and more preferably 1 × 10 -4 S / cm or more. The value of the ionic conductivity of the solid electrolyte can be measured by the alternating current impedance method.

[0028] Examples of the oxide solid electrolyte include compounds having a NASICON-type structure. Further examples of the oxide solid electrolyte include LiLaTiO (for example, Li 0.34 La 0.51 TiO3), LiPON (for example, Li 2.9 PO 3.3 N 0.46 ), LiLaZrO (for example, Li7La3Zr2O 12 ), etc.

[0029] The content of the solid electrolyte in the negative electrode active material layer is preferably in the range of 1 to 60% by mass, and more preferably in the range of 10 to 50% by mass.

[0030] In addition to the above-described negative electrode active material and solid electrolyte, the negative electrode active material layer may further contain at least one of a conductive assistant and a binder.

[0031] The thickness of the negative electrode active material layer varies depending on the configuration of the intended lithium secondary battery, but is preferably in the range of 0.1 to 1000 μm, for example.

[0032] [Solid electrolyte layer] In the stacked battery according to the embodiment shown in Figures 1 and 2, the solid electrolyte layer is a layer interposed between the above-described positive electrode active material layer and negative electrode active material layer, and essentially contains a solid electrolyte. There are no particular restrictions on the specific form of the solid electrolyte contained in the solid electrolyte layer, and the solid electrolytes exemplified in the section on the negative electrode active material layer and their preferred forms can be similarly employed. The solid electrolyte layer may further contain a binder in addition to the above-described predetermined solid electrolyte.

[0033] The thickness of the solid electrolyte layer varies depending on the configuration of the intended lithium secondary battery, but from the viewpoint of improving the volumetric energy density of the battery, it is preferably 600 μm or less, more preferably 500 μm or less, and even more preferably 400 μm or less. On the other hand, there is no particular restriction on the lower limit of the thickness of the solid electrolyte layer, but it is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more.

[0034] [Cathode active material layer] In the stacked battery according to the embodiment shown in FIGS. 1 and 2, the positive electrode active material layer contains a positive electrode material for an electric device according to one embodiment of the present invention. This positive electrode material for an electric device is characterized by having composite particles containing a sulfur-containing positive electrode active material in the pores of a porous conductor, and an electron conductor coating the surfaces of the composite particles. This configuration makes it possible to improve the cycle durability of an electric device using a sulfur-containing positive electrode active material. The mechanism by which this configuration provides such excellent effects is not fully understood, but the following mechanism is presumed. A preferred embodiment of this configuration will be described below with reference to the drawings.

[0035] FIG. 3 is a cross-sectional view of a cathode material 100′ according to the prior art. FIG. 4 is a cross-sectional view of a cathode material 100 according to one embodiment of the present invention. In FIGS. 3 and 4, a porous conductor (e.g., porous carbon) 110 has a large number of pores 110a. A cathode active material (e.g., sulfur) 120 is filled and disposed inside these pores 110a. Although not shown, the cathode active material 120 is also disposed on the surface of the porous conductor 110 in addition to the pores 110a.

[0036] As shown in FIG. 3, in a cathode material 100′ according to the prior art, the pores 110a are filled with a cathode active material 120 (state (a) in FIG. 3). During discharge, the cathode active material 120 expands by storing lithium ions. At this time, a portion of the cathode active material 120 that had been filled inside the pores 110a is pushed out of the pores 110a (state (B) in FIG. 3). During charge, the cathode active material 120 contracts by releasing lithium ions. As a result, the portion of the cathode active material 120 that had been pushed out of the pores 110a separates from the surface of the porous conductor 110, preventing electron transfer (state (C) in FIG. 3). In this way, repeated charge-discharge cycles increase the proportion of the cathode active material 120 that does not contribute to the charge-discharge reaction, and this reduces the cycle durability of an electrical device to which the cathode material 100′ is applied.

[0037] On the other hand, as shown in FIG. 4, in a cathode material 100 according to one embodiment of the present invention, the surfaces of composite particles formed by filling pores 110a with cathode active material 120 are coated with an electron conductor (e.g., graphene) (state (a) in FIG. 4). During discharge, the cathode active material 120 expands by storing lithium ions. At this time, a portion of the cathode active material 120 that had filled the pores 110a is pushed out of the pores 110a (state (B) in FIG. 4). During charge, the cathode active material 120 contracts by releasing lithium ions. In this case, in the embodiment shown in FIG. 4, even if a portion of the cathode active material 120 that had been pushed out of the pores 110a separates from the surface of the porous conductor 110, a conductive path is formed due to the presence of the electron conductor 130, and electrons can be transferred to and from the separated cathode active material 120 (state (C) in FIG. 4). As a result, even after repeated charge-discharge cycles, the proportion of the positive electrode active material 120 that does not contribute to the charge-discharge reaction is kept low, and therefore, the cycle durability of an electric device to which the positive electrode material 100 is applied is improved.

[0038] (porous conductor) Porous conductors are made of conductive materials and have pores (voids) inside. By filling the pores with a sulfur-containing cathode active material (described below), many contact points are formed between the pore walls and the cathode active material, and electrons are exchanged through these contact points. As a result, the utilization efficiency of the sulfur-containing cathode active material, which has low electron conductivity, can be improved, and the charge / discharge capacity can be increased.

[0039] The type of porous conductor is not particularly limited, and carbon materials, metal materials, conductive polymer materials, etc. can be appropriately employed, with carbon materials being preferred. Examples of carbon materials include activated carbon, Ketjen Black (registered trademark) (highly conductive carbon black), (oil) furnace black, channel black, thermal black, lamp black, and other carbon blacks; mesoporous carbon; coke; natural graphite; and carbon particles (carbon supports) made of artificial graphite. Among these, at least one material selected from the group consisting of activated carbon, carbon black, and mesoporous carbon is preferred, and at least one material selected from the group consisting of activated carbon and mesoporous carbon is more preferred. These carbon materials have sufficient pore sizes, making them easy to fill with sulfur-containing cathode active materials. It is preferable that the carbon material be primarily carbon. Here, "primarily carbon" refers to carbon containing carbon as the primary component, and encompasses both carbon atoms and carbon atoms alone. "Substantially carbon-containing" means that impurities of approximately 2 to 3% by mass or less can be tolerated.

[0040] The BET specific surface area of ​​the porous conductor (preferably a carbon material) is 200 m 2 / g or more is preferable, and 500m 2 / g or more is more preferable, and 800m 2 / g or more is more preferable, and 1200m 2 / g or more is particularly preferred, and 1500m 2It is most preferable that it is / g or more. Further, the pore volume of the porous conductor is preferably 1.0 mL / g or more, more preferably 1.3 mL / g or more, and even more preferably 1.5 mL / g or more. If the BET specific surface area and pore volume of the porous conductor are within the above ranges, a sufficient amount of pores can be retained, and thus a sufficient amount of the positive electrode active material can be retained. Note that the BET specific surface area and pore volume of the porous conductor can be measured by nitrogen adsorption / desorption measurement. This nitrogen adsorption / desorption measurement is performed using BELSORP mini manufactured by MicrotracBEL Corporation at a temperature of -196°C by the multi-point method. The BET specific surface area is determined from the adsorption isotherm in the relative pressure range of 0.01 < P / P0 < 0.05. Further, the pore volume is determined from the volume of adsorbed N2 at a relative pressure of 0.96.

[0041] The pore diameter (average pore diameter) of the porous conductor is not particularly limited, but the lower limit is preferably 0.5 nm or more, more preferably 1 nm or more, even more preferably 2 nm or more, and particularly preferably 5 nm or more. The upper limit is preferably 500 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less, and particularly preferably 30 nm or less. If the pore diameter is within the above range, electrons can be sufficiently supplied to the active material existing at a position away from the pore wall among the positive electrode active materials containing sulfur disposed inside the pores. Note that the pore diameter of the porous conductor can be calculated by nitrogen adsorption / desorption measurement as described above.

[0042] When the porous conductor is particulate, the average particle diameter (primary particle diameter) is not particularly limited, but is preferably 2 to 50 μm, more preferably 2 to 20 μm, and even more preferably 5 to 10 μm. In this specification, "particle diameter" refers to the longest distance L between any two points on the contour of a particle. The value of "average particle diameter" is calculated as the average particle diameter of particles observed in several to several tens of fields of view using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) (for example, the average particle diameter of 100 particles).

[0043] (Cathode active material) The cathode material according to this embodiment essentially contains a sulfur-containing cathode active material. The type of sulfur-containing cathode active material is not particularly limited, but includes, for example, elemental sulfur (S) and lithium sulfide (LiS), as well as particles or thin films of organic or inorganic sulfur compounds. Any material can be used as long as it utilizes the oxidation-reduction reaction of sulfur to release lithium ions during charging and absorb lithium ions during discharging. Inorganic sulfur compounds are particularly preferred due to their excellent stability. Specific examples include elemental sulfur (S), TiS, TiS, TiS, NiS, NiS, CuS, FeS, LiS, MoS, MoS, MnS, MnS, CoS, and CoS. Among these, S, Li2S, S-carbon composite, TiS2, TiS3, TiS4, FeS2 and MoS2 are preferred, and elemental sulfur (S) and lithium sulfide (Li2S), TiS2 and FeS2 are more preferred, with elemental sulfur (S) and lithium sulfide (Li2S) being particularly preferred from the viewpoint of high capacity.

[0044] The positive electrode material according to this embodiment may further contain a sulfur-free positive electrode active material in addition to the sulfur-containing positive electrode active material, provided that the proportion of the sulfur-containing positive electrode active material in the total amount (100% by mass) of the positive electrode active material is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass.

[0045] (electron conductor) The positive electrode material according to the present invention essentially contains an electron conductor. The electron conductor coats the surface of the composite particles, enabling electron transfer even to the positive electrode active material that has separated from the surface of the porous conductor due to charge and discharge. As a result, even after repeated charge and discharge cycles, the proportion of the positive electrode active material that does not contribute to the charge and discharge reaction is kept low, thereby improving the cycle durability of an electrical device incorporating the positive electrode material.

[0046] The type of electron conductor is not particularly limited as long as it has higher electron conductivity than the sulfur-containing positive electrode active material, but is preferably at least one selected from conductive carbon, metal, metal oxide, metal sulfide, and conductive polymer. Examples of conductive carbon include carbon fiber, graphene, carbon nanotubes (single-walled carbon nanotubes and multi-walled carbon nanotubes), carbon nanohorns, carbon nanoballoons, and fullerenes. Examples of metals include nickel, titanium, aluminum, copper, platinum, iron, chromium, tin, zinc, indium, antimony, and vanadium, as well as alloys containing at least one of these metals. Examples of alloys include stainless steel (SUS), Inconel (registered trademark), Hastelloy (registered trademark), and other Fe-Cr-based alloys and Ni-Cr alloys. Examples of metal oxides include titanium oxide (TiO2), zinc oxide (ZnO), indium oxide (In2O3), tin oxide (SnO2), indium tin oxide (ITO), vanadium oxide (VO5), triiron tetroxide (Fe3O4), zirconium oxide (ZrO2), and tungsten(IV) oxide (WO2). Examples of metal sulfides include iron sulfide (FeS), copper(I) sulfide (Cu2S), cadmium sulfide (CdS), and indium(III) sulfide (In2S3). Examples of conductive polymers include polycarbonate, polyaniline, polypyrrole, polythiophene (e.g., poly3,4-ethylenedioxythiophene (PDOT)), polyacetylene, polyparaphenylene, polyphenylenevinylene, polyacrylonitrile, and polyoxadia. Among these materials, at least one selected from the group consisting of conductive carbon and conductive polymer is preferred because it exhibits high electronic conductivity, at least one selected from the group consisting of conductive carbon is more preferred, carbon fiber, graphene, and carbon nanotubes (single-walled carbon nanotubes and multi-walled carbon nanotubes) are further preferred, and graphene is particularly preferred.

[0047] The shape of the electron conductor is not particularly limited, and particles, fibers, sheets, etc. can be appropriately used, but fibers or sheets are preferred from the viewpoint of good surface coverage of the composite particles. The size of the electron conductor is also not particularly limited, but from the viewpoint of good surface coverage of the composite particles, the preferred sizes of the electron conductor are as follows:

[0048] (1) When the electron conductor is fibrous (e.g., carbon fiber, carbon nanotube), the ratio of the pore size of the porous conductor to the average fiber length of the fibrous electron conductor is preferably greater than 0 and less than 1, more preferably greater than 0 and 0.1 or less, even more preferably greater than 0 and 0.01 or less, and particularly preferably 0.0001 or greater and 0.01 or less; or (2) The electron conductor is in the form of a sheet, and the ratio of the pore size of the porous conductor to the average longest diameter in the plane direction of the sheet-like electron conductor is preferably greater than 0 and less than 1, more preferably greater than 0 and 0.1 or less, even more preferably greater than 0 and 0.01 or less, and particularly preferably 0.0001 or more and 0.01 or less.

[0049] "The shape of the electronic conductor is fibrous" means that the average aspect ratio (length of the major axis / length of the minor axis) of the electronic conductor observed in several to several dozen fields of view using observation means such as SEM or TEM is 5 or more. Note that the average value here refers to the average value for, for example, 100 electronic conductors when the electronic conductor is particulate or fibrous. "The shape of the electronic conductor is sheet-like" means that the "ratio of the major axis in the plane direction to the thickness" and the "ratio of the minor axis in the plane direction to the thickness" observed using observation means such as SEM or TEM are each at least 100 or more.

[0050] The value of "average fiber length of fibrous electronic conductor" is calculated as the average value of the long axis lengths of fibrous electronic conductors observed in several to several dozen fields of view using observation means such as SEM or TEM (for example, the average value of the long axis lengths of 100 fibers).The value of "average thickness of sheet-like electronic conductor" is calculated as the average longest diameter in the plane direction of sheet-like electronic conductors observed in several to several dozen fields of view using observation means such as SEM or TEM (for example, the average value of the average longest diameter in the plane direction of 100 sheets).

[0051] In the positive electrode material according to this embodiment, the mass ratio of the electron conductor to the porous conductor is preferably greater than 0 and less than 1, more preferably 0.01 to 0.5, and even more preferably 0.1 to 0.5. When the mass ratio is greater than 0, the utilization efficiency of the sulfur-containing positive electrode active material can be further improved. When the ratio is less than 1, a decrease in charge / discharge capacity can be suppressed.

[0052] (electrolyte) The positive electrode material according to this embodiment preferably further contains an electrolyte in the pores of the porous conductor. By including an electrolyte, charge carriers can smoothly move in and out of the surface of the sulfur-containing positive electrode active material, thereby improving output characteristics. The specific form of the electrolyte is not particularly limited, and a liquid electrolyte or a solid electrolyte such as a sulfide solid electrolyte or an oxide solid electrolyte exemplified in the negative electrode active material layer section can be appropriately employed, but a solid electrolyte is preferred. When the electrolyte is a solid electrolyte, it is preferred that at least a portion of the solid electrolyte and at least a portion of the sulfur-containing positive electrode active material are disposed inside the pores of the porous conductor so as to be in contact with each other.

[0053] In particular, the solid electrolyte contained in the positive electrode material according to this embodiment is preferably a sulfide solid electrolyte. In another preferred embodiment, the sulfide solid electrolyte contains alkali metal atoms. Here, examples of alkali metal atoms that can be contained in the sulfide solid electrolyte include lithium atoms, sodium atoms, and potassium atoms. Among these, lithium atoms are preferred because of their excellent ionic conductivity. In yet another preferred embodiment, the solid electrolyte contained in the solid electrolyte layer contains alkali metal atoms (e.g., lithium atoms, sodium atoms, or potassium atoms; preferably lithium atoms) and phosphorus atoms and / or boron atoms. In one preferred embodiment, the sulfide solid electrolyte contains Li6PS5X (where X is Cl, Br, or I, preferably Cl). These solid electrolytes have high ionic conductivity and can therefore contribute particularly effectively to improving output characteristics.

[0054] An example of a method for producing a cathode material according to the present embodiment having the above-described configuration will be described. As described above, it is believed that the excellent cycle durability of the cathode material according to the present embodiment is due to the excellent formation of conductive paths by coating the surfaces of the composite particles with an electronic conductor. To achieve this configuration, the composite particles are first produced by the following method. First, a porous conductor and a sulfur-containing cathode active material are thoroughly mixed by mixing using a mixing means such as a mortar or by milling using a pulverizing means such as a planetary ball mill. The resulting mixture is then heat-treated at a high temperature. The heat treatment melts the sulfur-containing cathode active material, filling the pores of the porous conductor with the cathode active material. The heat treatment temperature is not particularly limited, but is preferably 170°C or higher, more preferably 175°C or higher, even more preferably 180°C or higher, and particularly preferably 185°C or higher. Meanwhile, the upper limit of the heat treatment temperature is also not particularly limited, but is, for example, 250°C or lower, preferably 200°C or lower. There is no particular restriction on the heat treatment time, but it may be about 1 to 5 hours.

[0055] When the composite particles further contain a solid electrolyte (e.g., a sulfide solid electrolyte) in the pores of the porous conductor, a manufacturing method may be employed in which a mixture of the porous conductor and the solid electrolyte is obtained by mixing or milling, and then a sulfur-containing cathode active material is added to the mixture, followed by the heat treatment described above. This method results in a preferable cathode material in which the cathode active material and the solid electrolyte penetrate into the pores of the porous conductor through the heat treatment, forming numerous three-phase interfaces. Another manufacturing method involves first preparing a solution in which the solid electrolyte is dissolved in a suitable solvent capable of dissolving the solid electrolyte. The porous conductor is then impregnated with the solution, and optionally heated at a temperature of approximately 100 to 180°C for approximately 1 to 5 hours to obtain a solid electrolyte-impregnated porous conductor. In this composite, the solid electrolyte typically penetrates and adheres to the pores of the porous conductor. Next, by adding an additional cathode active material containing sulfur to this composite and then subjecting it to the heat treatment described above, the cathode active material is melted and penetrates into the pores of the porous conductor, thereby obtaining composite particles with a preferable form in which numerous three-phase interfaces are formed. This manufacturing method using a wet process can produce composite particles with particularly excellent initial capacity characteristics and charge / discharge rate characteristics.

[0056] Next, the surfaces of the composite particles obtained by the above-mentioned manufacturing method are coated with an electronic conductor. Although the coating method is not particularly limited, it is preferable to adopt a mechanofusion method using a ball mill or the like. By such dry coating, the electronic conductor is physically adsorbed onto the surface of the composite particles, thereby forming a coating made of the electronic conductor on the surface of the composite particles. As an alternative method, the coating may be formed by coating the surface of the composite particles with an electronic conductor added with a binder.

[0057] The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but is preferably in the range of 35 to 99 mass %, more preferably in the range of 40 to 90 mass %, for example. Note that this content value is calculated based on the mass of only the positive electrode active material excluding the porous conductor and solid electrolyte.

[0058] The positive electrode active material layer may further contain a conductive additive (one that does not hold the positive electrode active material or solid electrolyte inside the pores) and / or a binder. Similarly, the positive electrode active material layer preferably further contains a solid electrolyte in addition to the above-mentioned positive electrode material.

[0059] The thickness of the positive electrode active material layer varies depending on the intended configuration of the lithium secondary battery, but is preferably within the range of 0.1 to 1000 μm, for example.

[0060] [Positive and negative current collector plates] The material constituting the current collector plates (25, 27) is not particularly limited, and known highly conductive materials conventionally used as current collector plates for secondary batteries can be used. Metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferred as constituent materials of the current collector plates. From the viewpoints of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferred, and aluminum is particularly preferred. The positive current collector plate 27 and the negative current collector plate 25 may be made of the same material or different materials.

[0061] [Positive and negative leads] Although not shown, the current collector and the current collecting plate may be electrically connected via a positive electrode lead and a negative electrode lead. Materials used in known secondary batteries may be used as the constituent materials of the positive electrode and negative electrode lead. It is preferable that the portion removed from the outer casing be covered with a heat-resistant, insulating heat-shrinkable tube or the like to prevent contact with peripheral devices or wiring, resulting in electrical leakage and affecting the product (e.g., automobile parts, particularly electronic devices).

[0062] [Battery exterior materials] As the battery exterior material, a known metal can case can be used, or a bag-shaped case using an aluminum-containing laminate film 29 that can cover the power-generating element as shown in Figures 1 and 2 can be used. The laminate film can be, for example, a three-layer laminate film formed by laminating PP, aluminum, and nylon in this order, but is not limited to these. A laminate film is desirable from the viewpoint of achieving high output and excellent cooling performance, making it suitable for use in batteries for large devices such as EVs and HEVs. Furthermore, an aluminum-containing laminate film is more preferable for the exterior body because it allows for easy adjustment of the collective pressure applied to the power-generating element from the outside.

[0063] The stacked battery according to the present embodiment has a configuration in which a plurality of unit cell layers are connected in parallel, and therefore has high capacity and excellent cycle durability, and is therefore suitable for use as a driving power source for EVs and HEVs.

[0064] The all-solid-state lithium secondary battery, which is one embodiment of an electric device, has been described above. However, the present invention is not limited to the configurations described in the above-described embodiment, and can be modified as appropriate based on the claims.

[0065] For example, the type of electric device to which the positive electrode material according to the present embodiment is applied includes a bipolar battery including a bipolar electrode having a positive electrode active material layer electrically coupled to one surface of a current collector and a negative electrode active material layer electrically coupled to the opposite surface of the current collector.

[0066] The electric device according to this embodiment does not have to be an all-solid-state lithium secondary battery. That is, the solid electrolyte layer may further contain a conventionally known liquid electrolyte (electrolytic solution). There is no particular limitation on the amount of liquid electrolyte (electrolytic solution) that can be contained in the solid electrolyte layer, but it is preferably an amount that allows the shape of the solid electrolyte layer formed by the solid electrolyte to be maintained and prevents leakage of the liquid electrolyte (electrolytic solution).

[0067] The lithium secondary battery to which the positive electrode material according to the present embodiment is applied is not limited to a laminated flat shape, and a wound lithium secondary battery may be a cylindrical shape or may be a cylindrical shape modified into a rectangular flat shape, and is not particularly limited.

[0068] [Battery pack] A battery pack is made up of multiple batteries connected together. Specifically, it is made up of at least two batteries connected in series, parallel, or both. By connecting them in series or parallel, it is possible to freely adjust the capacity and voltage.

[0069] A small, detachable assembled battery can be formed by connecting multiple batteries in series or in parallel. Furthermore, a large-capacity, high-output assembled battery (such as a battery module or battery pack) can be formed by further connecting multiple such small, detachable assembled batteries in series or in parallel, suitable for use as a vehicle drive power source or auxiliary power source, which require high volumetric energy density and high volumetric power density. The number of batteries to be connected to form a battery assembly and the number of stacked small assembled batteries to form a large-capacity assembled battery can be determined based on the battery capacity and output of the vehicle (electric vehicle) in which the battery will be installed.

[0070] [vehicle] A battery or a battery pack formed by combining a plurality of such batteries can be mounted on a vehicle. The present invention makes it possible to construct a long-life battery with excellent long-term reliability. By incorporating such a battery, a plug-in hybrid electric vehicle with a long EV driving range or an electric vehicle with a long driving range per charge can be constructed. For example, a battery or a battery pack formed by combining a plurality of such batteries can be used in a hybrid vehicle, a fuel cell vehicle, or an electric vehicle (all of which include four-wheeled vehicles (commercial vehicles such as passenger cars, trucks, and buses, and light vehicles), as well as two-wheeled vehicles (motorcycles) and three-wheeled vehicles) to produce a vehicle with a long life and high reliability. However, the application is not limited to automobiles, and the battery pack can also be applied to various power sources for other vehicles, such as trains, and can also be used as an on-board power source for uninterruptible power supplies and the like. [Example]

[0071] The present invention will be described in more detail below with reference to examples, although the technical scope of the present invention is not limited to the following examples.

[0072] <Example of test cell fabrication> [Example 1] (Preparation of solid electrolyte-impregnated porous conductor) In a glove box with an argon atmosphere (dew point below -68°C), 0.500 g of solid electrolyte (Ampcera, Li6PS5Cl) was added to 100 mL of ultra-dehydrated ethanol (Fujifilm Wako Pure Chemical Industries, Ltd.) and thoroughly stirred to dissolve the solid electrolyte in the ethanol. 1.00 g of porous conductor (porous carbon, average particle size 5 μm, pore size 30 nm) was added to the resulting solid electrolyte ethanol solution and thoroughly stirred to fully disperse the porous conductor in the solution. The container containing this dispersion was connected to a vacuum device, and the pressure in the container was reduced to below 1 Pa using an oil-sealed rotary pump while stirring the dispersion in the container with a magnetic stirrer. Because the solvent ethanol volatilizes under reduced pressure, the ethanol was removed over time, leaving the porous conductor impregnated with the solid electrolyte in the container. After removing the ethanol under reduced pressure, the container was heated to 180°C under reduced pressure for 3 hours to prepare a solid electrolyte-impregnated porous conductor.

[0073] (Preparation of composite particles) In a glove box with an argon atmosphere at a dew point of -68°C or below, 2.50g of sulfur (manufactured by Aldrich) as a positive electrode active material was added to 0.750g of the solid electrolyte-impregnated porous conductor prepared above and mixed thoroughly in an agate mortar. The mixed powder was then placed in a sealed pressure-resistant autoclave and heated at 170°C for 3 hours to melt the sulfur, thereby impregnating the solid electrolyte-impregnated porous conductor with sulfur. This produced composite particles in which the pores of the porous conductor were filled with sulfur and solid electrolyte.

[0074] (Preparation of positive electrode material) In a glove box with an argon atmosphere at a dew point of -68°C or below, the composite particles prepared above and an electronic conductor (graphene, average longest diameter in the plane direction: 5 μm) were mixed so that the mass ratio of the electronic conductor to the porous conductor in the composite particles was 0.01, and dry coating was performed using the mechanofusion method using a ball mill. Specifically, 5 mm zirconia balls were placed in a 250 mL zirconia ball mill pod, and the material was added under an argon atmosphere. The mixture was processed at 200 rpm for 4 hours to obtain a cathode material in which the surfaces of the composite particles were coated with the electronic conductor.

[0075] (Preparation of Positive Electrode Mixture) In a glove box with an argon atmosphere and a dew point of -68°C or less, 40 g of 5 mm diameter zirconia balls, 0.150 g of the positive electrode material, and 0.050 g of solid electrolyte (Li6PS5Cl, manufactured by Ampcera) were placed in a 45 ml zirconia container and milled at 370 rpm for 6 hours in a planetary ball mill (Premium line P-7, manufactured by Fritsch) to obtain a powder of the positive electrode mixture. The composition of the positive electrode mixture was positive electrode material:solid electrolyte = 75:25 (mass ratio).

[0076] (Production of test cells (all-solid-state lithium secondary batteries)) The battery was fabricated in a glove box with an argon atmosphere at a dew point of -68°C or below. A 10mm diameter stainless steel cylindrical punch was inserted into one side of a McCorm cylindrical tube jig (inner diameter 10mm, outer diameter 23mm, height 20mm), and 80mg of solid electrolyte (Ampcera, Li6PS5Cl) was placed from the top of the cylindrical tube jig. The other 10mm diameter stainless steel cylindrical punch was then inserted to sandwich the solid electrolyte. The tube was then pressed at 75MPa for 3 minutes using a hydraulic press to form a 10mm diameter, approximately 0.6mm thick solid electrolyte layer in the cylindrical tube jig. Next, the cylindrical convex punch inserted from above was removed, and 7.5 mg of the prepared positive electrode mixture was placed on one side of the solid electrolyte layer inside the cylindrical tube. A cylindrical convex punch (also serving as a positive electrode current collector) was inserted from above and pressed at a pressure of 300 MPa for 3 minutes to form a positive electrode active material layer with a diameter of 10 mm and a thickness of approximately 0.06 mm on one side of the solid electrolyte layer. Next, the lower cylindrical convex punch (also serving as a negative electrode current collector) was removed, and a lithium foil (manufactured by Nilaco Corporation, thickness 0.20 mm) punched to a diameter of 8 mm and an indium foil (manufactured by Nilaco Corporation, thickness 0.30 mm) punched to a diameter of 9 mm were stacked as negative electrodes. The cylindrical tube was inserted from the bottom of the cylindrical tube jig so that the indium foil was positioned next to the solid electrolyte layer. The cylindrical convex punch was then inserted again and pressed at a pressure of 75 MPa for 3 minutes to form a lithium-indium negative electrode. In this manner, a test cell (all-solid-state lithium secondary battery) was produced in which a negative electrode current collector (punch), a lithium-indium negative electrode, a solid electrolyte layer, a positive electrode active material layer, and a positive electrode current collector (punch) were stacked in this order.

[0077] [Example 2] A test cell was prepared in the same manner as in Example 1 above, except that the composite particles and the electronic conductor were mixed so that the mass ratio of the electronic conductor to the porous conductor in the composite particles was 0.05.

[0078] [Example 3] A test cell was prepared in the same manner as in Example 1 described above, except that the composite particles and the electronic conductor were mixed so that the mass ratio of the electronic conductor to the porous conductor in the composite particles was 0.1.

[0079] [Example 4] A test cell was prepared in the same manner as in Example 1 described above, except that the composite particles and the electronic conductor were mixed so that the mass ratio of the electronic conductor to the porous conductor in the composite particles was 0.2.

[0080] [Example 5] A test cell was prepared in the same manner as in Example 1 described above, except that the composite particles and the electronic conductor were mixed so that the mass ratio of the electronic conductor to the porous conductor in the composite particles was 0.5.

[0081] [Example 6] A test cell was produced in the same manner as in Example 3, except that carbon nanotubes (average fiber length: 5 μm) were used as the electron conductor instead of graphene.

[0082] [Example 7] A test cell was produced in the same manner as in Example 3, except that carbon fiber (average fiber length: 10 μm) was used as the electron conductor instead of graphene.

[0083] [Example 8] A test cell was produced in the same manner as in Example 1 above, except that porous carbon (average particle size: 4.8 μm, pore size: 1 nm) was used as the porous conductor.

[0084] [Example 9] A test cell was produced in the same manner as in Example 1 above, except that porous carbon (average particle size: 6 μm, pore size: 5 nm) was used as the porous conductor.

[0085] [Example 10] A test cell was produced in the same manner as in Example 1 above, except that porous carbon (average particle size: 5 μm, pore size: 100 nm) was used as the porous conductor.

[0086] [Example 11] A test cell was produced in the same manner as in Example 1 above, except that porous carbon (average particle size 5 μm, pore size 500 nm) was used as the porous conductor.

[0087] [Example 12] A test cell was produced in the same manner as in Example 3 above, except that PDOT (3,4-ethylenedioxythiophene) (average longest diameter: 5 μm) was used as the electron conductor instead of graphene.

[0088] [Example 13] A test cell was prepared in the same manner as in Example 1, except that graphene (average longest diameter: 2.5 μm) was used as the electronic conductor, and the composite particles and the electronic conductor were blended so that the mass ratio of the electronic conductor to the porous conductor in the composite particles was 15.

[0089] [Comparative Example 1] A test cell was prepared in the same manner as in Example 1 described above, except that acetylene black was used instead of porous carbon as the porous conductor, carbon fiber (average fiber length 10 μm) was used instead of graphene as the electron conductor, and the composite particles and electron conductor were blended so that the mass ratio of the electron conductor to the porous conductor in the composite particles was 0.1.

[0090] Comparative Example 2 A test cell was fabricated in the same manner as in Example 1 described above, except that porous carbon (average particle size 4.5 μm, pore size 4 nm) was used as the porous conductor and no electron conductor was used.

[0091] <Test cell evaluation example> The test cells prepared in the above examples and comparative examples were evaluated for capacity characteristics, resistance values, and cycle durability by the following methods. The evaluations were carried out using a charge-discharge tester (HJ-SD8, manufactured by Hokuto Denko Corporation) in a constant temperature bath set at 25°C.

[0092] (Capacitance characteristics) The test cell was placed in a thermostatic chamber, and after the cell temperature had stabilized, a current of 0.2 mA / cm was applied as cell conditioning. 2 The cell was discharged to a cell voltage of 0.5 V at a current density of 0.01 mA / cm. The cell was then subsequently charged to 2.5 V at a constant current and constant voltage with a cut-off current of 0.01 mA / cm. 2 This conditioning charge-discharge cycle was repeated 10 times, and the capacity value per mass of the positive electrode active material (mAh / g) was calculated from the charge-discharge capacity value obtained after this cycle and the mass of the positive electrode active material contained in the positive electrode.

[0093] (resistance value) The test cell was placed in a thermostatic chamber, and the cell's SOC (state of charge) was adjusted to 50%, and the current density was set to 0.2, 0.4, and 0.8 mA / cm. 2 The resistance was calculated from the IV curve obtained by varying the current and discharging for 30 seconds. Before applying the voltage at each current value, the voltage was adjusted to 0.2 mA / cm to achieve SOC 50%. 2 I charged it with.

[0094] (Cycle durability) One cycle consisted of a process of fully charging the battery at a constant current and constant voltage of 0.05 C-2.5 V with a cutoff current of 0.01 C, followed by discharging at a current density of 0.05 C with a cutoff voltage of 0.5 V. This cycle was repeated 100 times, and the capacity retention rate was calculated from the ratio of the 100th discharge capacity to the initial discharge capacity.

[0095] The results are shown in Table 1 below.

[0096] [Table 1]

[0097] The results shown in Table 1 demonstrate that, according to the present invention, an improvement in cycle durability can be achieved in an electric device using a positive electrode active material containing sulfur.

[0098] The use of graphene as an electron conductor leads to a higher capacity retention rate. This is thought to be due to the high electron conductivity of graphene. Also, the sheet-like nature of graphene allows for good coverage of the surfaces of the composite particles.

[0099] The smaller the ratio of the pore size of the porous conductor to the size of the electronic conductor (item "A / B" in Table 1), the better the capacity retention rate. This is thought to be because using an electronic conductor that is larger than the pore size of the porous conductor allows the surface of the composite particles to be well coated, further securing a conductive path between the positive electrode active material overflowing from the pores and the porous conductor.

[0100] The amount of the electronic conductor can be sufficiently improved even when it is relatively small (e.g., 0.01) relative to the amount of the porous conductor. This is thought to be because, even if the amount of the electronic conductor is small, the presence of the electronic conductor on the surface of the composite particles increases the amount of sulfur that can contribute to the charge-discharge reaction. Note that the capacity retention tends to improve as the amount of the electronic conductor increases. [Explanation of symbols]

[0101] 10a laminated battery, 11' negative electrode current collector, 11" positive electrode current collector, 13 negative electrode active material layer, 15 positive electrode active material layer, 17 solid electrolyte layer, 19 single cell layer, 21 power generation element, 25 negative electrode current collector, 27 positive electrode current collector, 29 laminate film, 100, 100' positive electrode material, 110 porous conductor (porous carbon), 110a pores, 120 positive electrode active material (sulfur), 130 electron conductor (graphene).

Claims

1. composite particles containing a positive electrode active material containing sulfur and a solid electrolyte in the pores of a porous conductor; an electron conductor coating the surface of the composite particle; and the porous conductor is in particulate form, the average primary particle diameter of the porous conductor is 2 to 50 μm; the electron conductor is at least one selected from the group consisting of carbon fiber, graphene, and carbon nanotube; the sulfur-containing positive electrode active material is in contact with the porous conductor within the pores of the porous conductor, A positive electrode material for an electric device, wherein the electron conductor is physically adsorbed onto the surface of the composite particle by dry coating, thereby forming a coating made of the electron conductor on the surface of the composite particle.

2. 2. The positive electrode material for an electrical device according to claim 1, wherein a mass ratio of the electronic conductor to the porous conductor is greater than 0 and less than 1.

3. The electron conductor is fibrous in shape, and the ratio of the pore diameter of the porous conductor to the average fiber length of the fibrous electron conductor is greater than 0 and less than 1; or 3. The positive electrode material for an electrical device according to claim 1, wherein the electron conductor has a sheet-like shape, and the ratio of the pore diameter of the porous conductor to the average longest diameter in the plane direction of the sheet-like electron conductor is greater than 0 and less than 1.

4. 4. The positive electrode material for an electric device according to claim 1, wherein at least a portion of the solid electrolyte and at least a portion of the sulfur-containing positive electrode active material are disposed inside pores of the porous conductor so as to be in contact with each other.

5. 5. The positive electrode material for an electric device according to claim 1, wherein the porous conductor has an average primary particle size of 5 to 50 μm.

6. 6. The positive electrode material for an electric device according to claim 1, wherein a mass ratio of said electron conductor to said porous electric conductor is 0.01 or more and 0.5 or less.

7. A positive electrode for an electric device, comprising the positive electrode material for an electric device according to any one of claims 1 to 6.

8. An electric device comprising the positive electrode for an electric device according to claim 7 .

9. The electrical device according to claim 8 , which is an all-solid-state lithium secondary battery.

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