Sulfide solid electrolyte composite and electrical device using same

Abstract

To provide means capable of suppressing the generation of hydrogen sulfide by improving the hydrolysis resistance of a sulfide solid electrolyte.SOLUTION: To form a sulfide solid electrolyte composite by supporting a sulfide solid electrolyte inside the pores of a porous material having pores.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sulfide solid electrolyte composite 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 on all-solid-state lithium secondary batteries using oxide-based or sulfide-based solid electrolytes has been actively conducted. Solid electrolytes are materials composed mainly of ionic conductors that can conduct ions in a solid state. Therefore, all-solid-state lithium secondary batteries do not, in principle, encounter the various problems caused by flammable organic electrolytes that are seen in conventional liquid-based lithium secondary batteries.

[0006] Among the solid electrolytes that can be used in all-solid-state batteries, sulfide solid electrolytes have attracted attention due to their high ionic conductivity, heat resistance, and stability under high voltage. However, sulfide solid electrolytes are highly reactive with water, and have the problem of generating toxic hydrogen sulfide when reacting with water. For this reason, a low dew point (dew point < -60°C) environment is required to handle sulfide solid electrolytes, and currently, glove boxes or super dry rooms are the only options.

[0007] Attempts have been made to suppress the generation of hydrogen sulfide due to contact of the above-mentioned sulfide solid electrolyte with water. For example, Patent Document 1 discloses a sulfide solid electrolyte containing an alkali metal element, phosphorus, sulfur, and a halogen, 31 A solid electrolyte has been proposed that has a peak in the region of 75.0 ppm to 80.0 ppm in the P-NMR spectrum. According to Patent Document 1, by using a sulfide solid electrolyte having such a composition, a solid electrolyte that is resistant to hydrolysis and has high ionic conductivity can be obtained. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-49834 Summary of the Invention [Problem to be solved by the invention]

[0009] However, even the solid electrolyte described in Patent Document 1 does not have sufficient resistance to hydrolysis in an environment with humidity similar to that of the atmosphere (humidity 80 to 90% RH, temperature 25°C), as shown in Figures 2 and 3 of Patent Document 1. Therefore, there is still a problem of generating a large amount of hydrogen sulfide.

[0010] Therefore, an object of the present invention is to provide a means for improving the hydrolysis resistance of a sulfide solid electrolyte and suppressing the generation of hydrogen sulfide. [Means for solving the problem]

[0011] 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 supporting a sulfide solid electrolyte inside the pores of a porous material having pores, thereby completing the present invention.

[0012] One aspect of the present invention is a sulfide solid electrolyte composite including a porous material having pores and a sulfide solid electrolyte supported inside the pores. [Effects of the Invention]

[0013] According to the present invention, it is possible to improve the hydrolysis resistance of the sulfide solid electrolyte and suppress the generation of hydrogen sulfide. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional schematic view of a sulfide solid electrolyte composite according to one embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing the appearance of a flat laminated type all-solid-state lithium secondary battery, which is one embodiment of the lithium secondary battery according to the present invention. [Figure 3] FIG. 3 is a cross-sectional view taken along line 2-2 shown in FIG. [Figure 4] FIG. 1 is a schematic diagram of a device for measuring the amount of hydrogen sulfide generated from a sulfide solid electrolyte composite prepared in an example. DETAILED DESCRIPTION OF THE INVENTION

[0015] One embodiment of the present invention is a sulfide solid electrolyte composite including a porous material having pores and a sulfide solid electrolyte supported inside the pores. The sulfide solid electrolyte composite of this embodiment can improve the hydrolysis resistance of the sulfide solid electrolyte and suppress the generation of hydrogen sulfide. Figure 1 shows a cross-sectional schematic diagram of a sulfide solid electrolyte composite according to one embodiment of the present invention.

[0016] The sulfide solid electrolytes used in all-solid-state batteries offer high ionic conductivity, but are highly reactive with water. For example, the residual Li2S (free Li2S) that is generated during the preparation of sulfide solid electrolytes, and the P2S7 portion of sulfide solid electrolytes with a Li4P2S7 skeleton, are thought to undergo hydrolysis as shown in the following formula when they come into contact with water vapor, resulting in a decrease in ionic conductivity. Another problem is that this hydrolysis generates toxic hydrogen sulfide (H2S).

[0017] [ka]

[0018] For this reason, a low dew point environment (dew point < -60°C) is required to handle sulfide solid electrolytes, and currently there is no choice but to use a glove box or super dry room.

[0019] 1, in the sulfide solid electrolyte composite 100 of this embodiment, the sulfide solid electrolyte 130 is disposed inside the pores 110a of the porous material 110. By disposing the sulfide solid electrolyte 130 inside the pores 110a of the porous material 110, contact between water vapor and the sulfide solid electrolyte 130 can be reduced. As a result, it is believed that the hydrolysis resistance of the sulfide solid electrolyte 130 can be improved.

[0020] Furthermore, at the contact interface 140 between the porous material 110 and the sulfide solid electrolyte 130, the sulfide solid electrolyte 130 can be stabilized by a reaction between the surface functional groups of the porous material 110 and the sulfide solid electrolyte 130. For example, the sulfide solid electrolyte 130 is stabilized by reacting free Li2S with the surface hydroxyl groups (-OH) of the porous material 110, as shown in the following formula:

[0021] [ka]

[0022] Furthermore, for example, as shown in the following formula, the PSP bond that is easily hydrolyzed in the sulfide solid electrolyte 130 reacts with the surface hydroxyl groups of the porous material 110 and is stabilized.

[0023] [ka]

[0024] Therefore, it is believed that the stabilization of the sulfide solid electrolyte 130 through such a reaction with the surface functional groups of the porous material 110 can also improve the hydrolysis resistance.

[0025] As described above, according to the sulfide solid electrolyte composite of this embodiment, by supporting the sulfide solid electrolyte in the pores of a porous material, it is possible to significantly improve hydrolysis resistance without modifying the sulfide solid electrolyte itself. Therefore, the sulfide solid electrolyte composite of this embodiment can be used even in high dew point environments that have not been possible with conventional sulfide solid electrolyte composites. Furthermore, since contact between the sulfide solid electrolytes is ensured, the ionic conductivity of the sulfide solid electrolyte is not significantly impaired.

[0026] [Sulfide solid electrolyte composite] The components of the sulfide solid electrolyte composite will be described below.

[0027] (Porous materials with pores) The sulfide solid electrolyte composite according to this embodiment essentially contains a porous material having pores. The specific form of the porous material contained in the sulfide solid electrolyte composite according to this embodiment is not particularly limited as long as it has pores, and conventionally known materials can be appropriately used. The shape of the porous material having pores is also not particularly limited, and it can be any shape such as particles, sheets, or thin films.

[0028] The material of the porous material having pores is not particularly limited and can be appropriately selected depending on the purpose. For example, when an insulating material is used as the porous material, the sulfide solid electrolyte composite according to the present embodiment can be used as a solid electrolyte for an electrolyte layer or an electrode active material layer (a positive electrode active material layer or a negative electrode active material layer). When an electronically conductive material is used as the porous material, the sulfide solid electrolyte composite according to the present embodiment can be used as a solid electrolyte for an electrode active material layer. When the porous material is used as an electrode active material layer, it is more preferable that the porous material be electronically conductive, since the porous material also functions as an electron conduction path. When the sulfide solid electrolyte composite according to the present embodiment is used as a porous material having ion conductivity, the sulfide solid electrolyte composite according to the present embodiment can be used as a solid electrolyte for an electrolyte layer or an electrode active material layer.

[0029] The insulating material is not particularly limited, but examples include inorganic materials such as oxides (SiO2, Al2O3, ZrO2, TiO2), hydroxides, and nitrides of silicon, aluminum, zirconium, and titanium, as well as composites thereof. Among these, metal oxide materials such as silica, alumina, titania, and zirconia are preferred because of their excellent strength, ease of processing, and ease of designing a desired pore distribution. Porous materials such as monoliths can be used. For example, porous materials such as titania monoliths and silica monoliths, which have a two-stage hierarchical structure consisting of through-holes of approximately 0.15 to 5 μm and pores of 100 nm or less, are preferred. Alternatively, porous materials can be used that are formed by molding particles of inorganic materials, optionally with a binder, into a porous structure.

[0030] Alternatively, the insulating porous material may be a porous sheet made of polymer or fiber. Specific examples of the porous sheet made of polymer or fiber include porous sheets made of polyolefins such as polyethylene (PE) and polypropylene (PP), hydrocarbon resins such as polyimide, aramid, and polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), and glass fibers.

[0031] As the electron-conductive porous material, a carbon material having pores is preferred from the viewpoints of excellent electron conductivity, ease of processing, and ease of designing a desired pore distribution.

[0032] Examples of carbon materials having micropores include activated carbon, Ketjen Black (registered trademark) (highly conductive carbon black), (oil) furnace black, channel black, acetylene black, thermal black, lamp black, and other carbon blacks; carbon particles (carbon supports) made from coke, natural graphite, artificial graphite, and the like. Commercially available porous carbons, such as Knobel (registered trademark) manufactured by Toyo Tanso Co., Ltd., which have numerous mesopores and interconnected pores, can also be used as carbon materials having micropores. Alternatively, a ceramic or other mold and a carbon raw material such as a resin may be mixed and fired under an inert atmosphere. The mold may then be dissolved with acid to synthesize a carbon material having a porous structure in which the shape of the mold has been transferred. This carbon material may then be used. The pore size and pore volume of the resulting carbon material can be controlled by appropriately adjusting the particle size of the mold and the blending ratio of the carbon raw materials. It is preferable that the carbon material be primarily composed of carbon. Here, "mainly composed of carbon" means that carbon atoms are contained as the main component, and is a concept that includes both "consisting only of carbon atoms" and "consisting essentially of carbon atoms." "Consisting essentially of carbon atoms" means that the inclusion of impurities of about 2 to 3 mass % or less is acceptable.

[0033] The ion-conductive porous material is not particularly limited, but examples thereof include compounds having a NASICON structure, which is an oxide solid electrolyte. An example of a compound having a NASICON structure is a compound represented by the general formula Li 1+x Al x Ge 2-x Compounds (LAGP) represented by (PO4)3 (0≦x≦2), general formula Li 1+x Al x Ti 2-xCompounds represented by (PO4)3 (0 ≦ x ≦ 2) such as (LATP) can be mentioned. Further, as other examples of the oxide solid electrolyte, 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. can be mentioned.

[0034] The BET specific surface area of the porous material having pores (preferably, a carbon material) is preferably 200 m 2 / g or more, more preferably 500 m 2 / g or more, still more preferably 800 m 2 / g or more, particularly preferably 1200 m 2 / g or more, and most preferably 1500 m 2 / g or more. Further, the total pore volume of the porous material having pores (preferably, a carbon material) is not particularly limited, but is preferably 0.50 cm 3 / g or more, more preferably 1.0 cm 3 / g or more, still more preferably 1.3 cm 3 / g or more, and further preferably 1.5 cm 3 / g or more. If the BET specific surface area and the total pore volume of the porous material are within such ranges, a sufficient amount of pores can be retained, and thus a sufficient amount of the sulfide solid electrolyte can be retained. Note that the values of the BET specific surface area and the total pore volume of the porous material 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 total pore volume is determined from the volume of adsorbed N2 at a relative pressure of 0.96.

[0035] The average pore diameter of the porous material is not particularly limited, but is preferably 1 μm or less. When the average pore diameter of the porous material is 1 μm or less, ion conduction paths are more uniformly formed due to the interconnection of the solid electrolyte filled in the pores, thereby suppressing the occurrence of anisotropy and uneven distribution of ion conduction. The average pore diameter of the porous material can be calculated by nitrogen adsorption / desorption measurement, as in the case of determining the BET specific surface area and total pore volume. When the porous material is a carbon material, the average pore diameter is more preferably 50 nm or less, and particularly preferably 30 nm or less. When the porous material is a porous body having a two-stage hierarchical structure of through pores and micropores, it is more preferable that the average through pore diameter of the through pores is 1 μm or less, and the average pore diameter of the micropores is 50 nm or less.

[0036] The pore volume ratio (porosity) of the porous material is not particularly limited, but is preferably 30 to 95%. A pore volume ratio of 30% or more allows a sufficient number of pores to be retained, and therefore a sufficient amount of sulfide solid electrolyte to be retained. Furthermore, a pore volume ratio of 95% or less is preferable because it increases the contact surface between the solid electrolyte and the porous material, sufficiently reduces contact between the solid electrolyte and the atmosphere, and provides sufficient mechanical strength. The pore volume ratio is the pore volume ratio of the porous material before the sulfide solid electrolyte is introduced. The pore volume ratio can be determined from the total pore volume and specific gravity of the porous material.

[0037] When the porous material is particulate, the average particle size (primary particle size) is not particularly limited, but is preferably 0.05 to 50 μm, more preferably 0.1 to 20 μm, and even more preferably 0.5 to 10 μm. The "average particle size of the porous material" is calculated as the average particle size of particles observed in several to several tens of fields of view using an observation tool such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). When the porous material is in the form of a sheet or thin film, the thickness is also not particularly limited, and can be, for example, 10 to 1000 μm.

[0038] (Sulfide solid electrolyte) The sulfide solid electrolyte is not particularly limited, but preferably contains an alkali metal atom. Examples of alkali metal atoms include Li, Na, and K atoms, with Li atoms being preferred because of their excellent ionic conductivity. The sulfide solid electrolyte preferably contains an alkali metal atom and a phosphorus atom and / or a boron atom. These sulfide solid electrolytes have high ionic conductivity, and therefore can effectively contribute to the realization of the effects of the present invention. Examples of sulfide solid electrolytes containing such alkali metal atoms and phosphorus and / or boron atoms include LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, LiI-Li3PS4, LiI-LiBr-Li3PS4, Li3PS4, Li2S-P2S5, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li2S-SiS2-Li3PO4, etc. 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.

[0039] 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 and LiI-LiBr-Li3PS 4、 Examples of sulfide solid electrolytes having a Li4P2S7 skeleton include Li-PS-based solid electrolytes called LPS (e.g., 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 them, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing P element, and more preferably 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).

[0040] Also, when the sulfide solid electrolyte is of the Li2S-P2S5 system, the ratio of Li2S and P2S5 is preferably within the range of Li2S:P2S5 = 50:50 to 100:0 in terms of molar ratio, and more preferably Li2S:P2S5 = 70:30 to 80:20.

[0041] Also, the sulfide solid electrolyte may be a sulfide glass, a crystallized sulfide glass, or a crystalline material obtained by a solid-phase method. The sulfide glass can be obtained, for example, by performing mechanical milling (such as a ball mill) on a raw material composition. Also, the crystallized sulfide glass can be obtained, for example, by performing heat treatment on the sulfide glass at a temperature above the crystallization temperature. 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, preferably, 1×10 -4 S / cm or more, more preferably 5×10 -4 S / cm or more, even more preferably 1×10 -3 S / cm or more. The value of the ionic conductivity of the sulfide solid electrolyte can be measured by an alternating current impedance method.

[0042] In the sulfide solid electrolyte composite of this embodiment, the pores are preferably filled only with the sulfide solid electrolyte. This allows the effects of the present invention to be more pronounced. More preferably, the pores of the sulfide solid electrolyte composite of this embodiment are filled only with a sulfide solid electrolyte containing alkali metal atoms and phosphorus and / or boron atoms. In addition, the pores of the sulfide solid electrolyte composite of this embodiment are preferably not filled with an electrode active material (positive electrode active material, negative electrode active material). In the sulfide solid electrolyte composite of this embodiment, of the components filling the pores of the porous material, preferably 95 mass % or more is the sulfide solid electrolyte, more preferably 99 mass % or more is the sulfide solid electrolyte, and most preferably 100 mass % is the sulfide solid electrolyte.

[0043] The sulfide solid electrolyte composite of this embodiment is not particularly limited, but the mass proportion of the sulfide solid electrolyte relative to the total amount of the porous material and the sulfide solid electrolyte is preferably 20 to 90 mass%, more preferably 40 to 90 mass%, even more preferably 70 to 90 mass%, and even more preferably 80 to 90 mass%. When the mass proportion of the sulfide solid electrolyte is 20 mass% or more, excellent ion conductivity can be ensured. Furthermore, when it is 90 mass% or less, the effect of suppressing the generation of hydrogen sulfide is more excellent. In particular, when the porous material is a carbon material, the above range is preferable.

[0044] The sulfide solid electrolyte composite of this embodiment is not particularly limited, but the volume V of the pores of the porous material p volume of sulfide solid electrolyte V el The ratio (V el / V p ) is preferably 0.8 or more, more preferably 1.0 or more. When it is in the above range, the effects of the present invention can be more significantly obtained. el / V p The upper limit of the pore volume V of the porous material is not particularly limited, but is, for example, 2.0 or less, and preferably 1.5 or less. p volume of sulfide solid electrolyte V elThe ratio (V el / V p ) is the mass (g) of the sulfide solid electrolyte charged in the preparation of the sulfide solid electrolyte composite and the specific gravity (g / cm 3 ) and the volume of the sulfide solid electrolyte, V, calculated from el (cm 3 ) and the total pore volume (cm) of the porous material measured by nitrogen adsorption / desorption method. 3 / g) and the charged mass (g) of the porous material, V p (cm 3 ) and can be found from

[0045] The sulfide solid electrolyte composite of this embodiment has an ionic conductivity (e.g., Li ion conductivity) of, for example, 1×10 -5 S / cm or more is preferable, and 1×10 -4 S / cm or more is more preferable, and 5×10 -4 S / cm or more is more preferable, and 1×10 -3 It is even more preferable that the ionic conductivity of the sulfide solid electrolyte composite is 1000 s / cm or more. The ionic conductivity of the sulfide solid electrolyte composite can be measured by an AC impedance method.

[0046] Although there are no particular limitations on the method for producing the sulfide solid electrolyte composite according to this embodiment having the above-described configuration, an example of the production method will be briefly described. As described in the Examples section below, first, a solution is prepared by dissolving a sulfide solid electrolyte in an organic solvent, and a particulate porous material is dispersed therein to obtain a dispersion. Alternatively, a sheet-shaped porous material is immersed. In this case, the amounts of the sulfide solid electrolyte and porous material used may be set so that the mass ratio of the sulfide solid electrolyte to the total amount of the porous material and the sulfide solid electrolyte in the sulfide solid electrolyte composite falls within the above-described range. Next, the solvent is removed, preferably under reduced pressure, and the resulting product is subjected to heat treatment at a temperature of approximately 150 to 450°C for approximately 1 to 5 hours. This results in a sulfide solid electrolyte composite in which the sulfide solid electrolyte is disposed (filled) inside the pores of the porous material.

[0047] The organic solvent is not particularly limited, but examples include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, glycerin, capryl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, oleyl alcohol, and linolyl alcohol; ethers such as diethyl ether, tetrahydrofuran, 1,4-dioxane, and 1,3-dioxolane; and acetonitrile. The water content of the solvent is preferably less than 0.2% by mass. More preferably, the water content of the solvent is 0.1% by mass or less, even more preferably 0.05% by mass or less, even more preferably 0.02% by mass or less, even more preferably 0.01% by mass or less, even more preferably 0.005% by mass or less, and particularly preferably 0.002% by mass or less. The water content of the solvent can be measured, for example, by Karl Fischer coulometric titration.

[0048] The step of preparing a solution by dissolving a sulfide solid electrolyte in an organic solvent, the step of dispersing a particulate porous material in the solution to obtain a dispersion, or the step of immersing a sheet-shaped porous material in the solution are preferably carried out in an inert gas atmosphere with a controlled dew point, for example, an inert gas atmosphere with a dew point of less than −60° C., preferably −60° C. or lower.

[0049] Here, whether or not a sulfide solid electrolyte is disposed inside the pores of a porous material having pores can be confirmed using various conventionally known methods. For example, an image of a cross section of a porous material observed with a transmission electron microscope (TEM) is subjected to elemental mapping of each material using energy dispersive X-ray spectroscopy (EDX). The arrangement of each material can then be confirmed using the obtained elemental map and the count number of each element relative to the count number of all elements as indicators.

[0050] Hereinafter, with reference to the drawings, a secondary battery will be described as an example of an electrical device using the sulfide solid electrolyte composite of the present invention. Note that the dimensional proportions in the drawings are exaggerated for the sake of convenience and may differ from the actual proportions. Below, the present invention will be described using a stacked-type (internal parallel connection) all-solid-state lithium secondary battery, which is one form of secondary battery. As described above, the solid electrolyte constituting an all-solid-state lithium secondary battery is a material composed mainly 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 various problems caused by flammable organic electrolytes, as in conventional liquid-based lithium secondary batteries. Furthermore, generally, the use of a high-potential, high-capacity positive electrode material and a high-capacity negative electrode material has the advantage of significantly improving the output density and energy density of the battery.

[0051] FIG. 2 is a perspective view showing the appearance of a flat-laminated all-solid-state lithium secondary battery, which is one embodiment of the sulfide solid electrolyte composite according to the present invention. FIG. 3 is a cross-sectional view taken along line 2-2 in FIG. 2. The laminated structure allows the battery to be compact and have a high capacity. In this specification, the flat-laminated non-bipolar lithium secondary battery shown in FIGS. 2 and 3 (hereinafter also simply referred to as a "laminated battery") will be described in detail as an example. However, in terms of the internal electrical connection configuration (electrode structure) of the lithium secondary battery according to this embodiment, it can be applied to both non-bipolar (internal parallel connection type) batteries and bipolar (internal series connection type) batteries.

[0052] 2, 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.

[0053] The lithium secondary battery according to this embodiment is not limited to a laminated, flat shape. A wound lithium secondary battery may be cylindrical, or may be a cylindrical battery modified into a rectangular, flat shape, and is not particularly limited. The cylindrical battery may use a laminate film or a conventional cylindrical can (metal can) as its exterior material, and is not particularly limited. Preferably, the power generating element is housed inside a laminate film containing aluminum. This configuration can achieve weight reduction.

[0054] There are also no particular limitations on how the current collectors (25, 27) shown in Fig. 2 are pulled out. The negative current collector 25 and the positive current collector 27 may be pulled out from the same side, or the negative current collector 25 and the positive current collector 27 may each be divided into multiple pieces and pulled out from each side, and so on, and are not limited to what is shown in Fig. 2. In addition, in a wound-type lithium battery, terminals may be formed using, for example, a cylindrical can (metal can) instead of tabs.

[0055] 3, the stacked battery 10a of this embodiment has a structure in which a flat, generally 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 stacked. 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'. Specifically, the positive electrode, solid electrolyte layer, and negative electrode are stacked in this order such that one positive electrode active material layer 15 faces the adjacent negative electrode active material layer 13 with the solid electrolyte layer 17 interposed therebetween. As a result, the adjacent positive electrode, solid electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the stacked battery 10a shown in FIG. 3 has a structure in which a plurality of unit cell layers 19 are stacked and electrically connected in parallel.

[0056] As shown in FIG. 3, the outermost positive electrode current collectors located on both outermost layers of the power generating element 21 each have a positive electrode active material layer 15 disposed on only one side, but active material layers may be provided on both sides. That is, instead of using a current collector exclusively for the outermost layer with an active material layer provided on only one side, a current collector having active material layers on both sides may be used as the outermost current collector. In some cases, the negative electrode active material layer 13 and the positive electrode active material layer 15 may be used as the negative electrode and the positive electrode, respectively, without using the current collectors (11', 11")

[0057] 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.

[0058] The main components of the lithium secondary battery according to this embodiment will be described below.

[0059] [Current collector] The current collector has a function of mediating the transfer of electrons from the electrode active material layer. There are no particular limitations on the material constituting the current collector. For example, metals and conductive resins can be used as the material constituting the current collector.

[0060] Specifically, examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. Other examples include clad materials of nickel and aluminum, and clad materials of copper and aluminum. Furthermore, foils in which aluminum is coated on a metal surface may also be used. Among these, aluminum, stainless steel, copper, and nickel are preferred from the viewpoints of electronic conductivity, battery operating potential, and adhesion of the negative electrode active material to the current collector by sputtering.

[0061] The latter conductive resin may be a resin in which a conductive filler is added to a non-conductive polymer material.

[0062] Examples of non-conductive polymeric materials include polyethylene (PE; high-density polyethylene (HDPE), low-density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), and polystyrene (PS). Such non-conductive polymeric materials can have excellent potential resistance or solvent resistance.

[0063] The conductive filler can be any material that is conductive. Examples of materials with excellent conductivity, potential resistance, or lithium ion blocking properties include metals and conductive carbon. While there are no particular limitations on the metal, it is preferable to use at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, and Sb, or an alloy or metal oxide containing such a metal. Furthermore, there are no particular limitations on the conductive carbon. Preferably, the conductive carbon contains at least one selected from the group consisting of acetylene black, Vulcan®, Black Pearl®, carbon nanofiber, Ketjen Black®, carbon nanotubes, carbon nanohorns, carbon nanoballoons, and fullerenes.

[0064] The amount of conductive filler added is not particularly limited as long as it is an amount that can impart sufficient conductivity to the current collector, and is generally 5 to 80 mass % relative to the total mass of the current collector (100 mass %).

[0065] The current collector may have a single layer structure made of a single material, or may have a laminate structure made of an appropriate combination of layers made of these materials. From the viewpoint of reducing the weight of the current collector, it is preferable that the current collector includes at least a conductive resin layer made of a resin having electrical conductivity. Furthermore, from the viewpoint of blocking the movement of lithium ions between the cell layers, a metal layer may be provided on a part of the current collector. Furthermore, if the negative electrode active material layer and the positive electrode active material layer described later are electrically conductive and can perform a current collecting function, it is not necessary to use a current collector as a separate member from these electrode active material layers. In such a configuration, the negative electrode active material layer described later constitutes the negative electrode, and the positive electrode active material layer described later constitutes the positive electrode.

[0066] [Negative electrode (negative electrode active material layer)] In the stacked battery according to the embodiment shown in FIGS. 2 and 3, 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 thereof include carbon materials, metal oxides, and metal active materials. Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of metal oxides include Nb2O5, Li4Ti5O 12 and the like. Furthermore, silicon-based negative electrode active materials and tin-based negative electrode active materials may also be used. Here, silicon and tin belong to the 14th group of elements, and are known to be negative electrode active materials that can significantly improve the capacity of non-aqueous electrolyte secondary batteries. These simple substances can absorb and release a large number of charge carriers (lithium ions, etc.) per unit volume (mass), and therefore become high-capacity negative electrode active materials. Here, it is preferable to use Si simple substance as the silicon-based negative electrode active material. Similarly, SiO 2 disproportionated into two phases, an Si phase and a silicon oxide phase, is also used. xIt is also preferable to use silicon oxides such as (0.3≦x≦1.6). In this case, the range of x is more preferably 0.5≦x≦1.5, and even more preferably 0.7≦x≦1.2. Furthermore, an alloy containing silicon (silicon-containing alloy-based negative electrode active material) may be used. On the other hand, examples of negative electrode active materials containing tin element (tin-based negative electrode active materials) include simple Sn, tin alloys (Cu—Sn alloy, Co—Sn alloy), amorphous tin oxide, tin silicon oxide, etc. Among these, examples of amorphous tin oxide include SnB 0.4 P 0.6 O 3.1 Examples of tin silicon oxides include SnSiO3. A metal containing lithium 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 an active material containing lithium, and examples thereof include metallic lithium and lithium-containing alloys. Examples of lithium-containing alloys include alloys of Li and at least one of In, Al, Si, and Sn. In some cases, two or more negative electrode active materials may be used in combination. Of course, negative electrode active materials other than those mentioned above may also be used. The negative electrode active material preferably contains metallic lithium, a silicon-based negative electrode active material, or a tin-based negative electrode active material, and particularly preferably contains metallic lithium.

[0067] The shape of the negative electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. When the negative electrode active material is particulate, its average particle diameter (D 50 ) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. In this specification, the average particle diameter (D 50 The value of can be measured by a laser diffraction scattering method.

[0068] 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.

[0069] The negative electrode active material layer may further include a solid electrolyte. The inclusion of a solid electrolyte in the negative electrode active material layer can improve the ionic conductivity of the negative electrode active material layer. Examples of solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes, with sulfide solid electrolytes being preferred. Preferably, the negative electrode active material layer includes the sulfide solid electrolyte composite of this embodiment (using an electronically conductive porous material) as the solid electrolyte. This improves the hydrolysis resistance of the sulfide solid electrolyte and suppresses the generation of hydrogen sulfide. This enables handling even in high dew-point environments where conventional materials could not be used. Furthermore, the electronically conductive porous material also functions as an electron conduction path, improving the electronic conductivity of the negative electrode active material layer.

[0070] The content of the solid electrolyte in the negative electrode active material layer is, for example, preferably in the range of 1 to 60 mass %, more preferably in the range of 10 to 50 mass %. When the sulfide solid electrolyte composite of this embodiment is included, this content value is calculated based on the mass of only the solid electrolyte excluding the porous material.

[0071] The negative electrode active material layer may further contain at least one of a conductive additive and a binder in addition to the above-mentioned negative electrode active material and solid electrolyte.

[0072] Examples of conductive additives include, but are not limited to, metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium; alloys or metal oxides containing these metals; carbon fibers (specifically, vapor-grown carbon fibers (VGCF), polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, activated carbon fibers, etc.); carbon nanotubes (CNTs); and carbon black (specifically, acetylene black, Ketjen Black (registered trademark), furnace black, channel black, thermal lamp black, etc.). Furthermore, particulate ceramic materials or resin materials coated with the above-mentioned metal materials by plating or the like can also be used as conductive additives. Among these conductive additives, from the viewpoint of electrical stability, it is preferable to include at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon, more preferably at least one selected from the group consisting of aluminum, stainless steel, silver, gold, and carbon, and even more preferably at least one carbon. These conductive additives may be used alone or in combination. The concept of the conductive additive does not include those that have pores but hold a solid electrolyte inside the pores.

[0073] The conductive additive is preferably in the form of particles or fibers. When the conductive additive is in the form of particles, the shape of the particles is not particularly limited, and may be any shape such as powder, sphere, rod, needle, plate, column, irregular shape, scale, or spindle shape.

[0074] When the conductive additive is particulate, its average particle size (primary particle size) is not particularly limited, but is preferably 0.01 to 10 μm from the viewpoint of the electrical properties of the battery. In this specification, the "particle size of the conductive additive" refers to the longest distance L between any two points on the contour line of the conductive additive. The value of the "average particle size of the conductive additive" is calculated as the average particle size 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).

[0075] When the negative electrode active material layer contains a conductive additive, the content of the conductive additive in the negative electrode active material layer is not particularly limited, but is preferably 0 to 10 mass %, more preferably 2 to 8 mass %, and even more preferably 4 to 7 mass %, relative to the total mass of the negative electrode active material layer. Within such a range, a stronger electron conduction path can be formed in the negative electrode active material layer, which can effectively contribute to improving battery characteristics.

[0076] On the other hand, the binder is not particularly limited, but examples thereof include the following materials: Thermoplastic polymers such as polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyethernitrile, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR), ethylene-propylene-diene copolymer, styrene-butadiene-styrene block copolymer and its hydrogenated products, styrene-isoprene-styrene block copolymer and its hydrogenated products, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene Examples of such fluororesins include ethylene-chlorotrifluoroethylene copolymer (ECTFE) and polyvinyl fluoride (PVF), vinylidene fluoride-based fluororubbers such as vinylidene fluoride-hexafluoropropylene-based fluororubbers (VDF-HFP-based fluororubbers), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubbers (VDF-HFP-TFE-based fluororubbers), vinylidene fluoride-pentafluoropropylene-based fluororubbers (VDF-PFP-based fluororubbers), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubbers (VDF-PFP-TFE-based fluororubbers), vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene-based fluororubbers (VDF-PFMVE-TFE-based fluororubbers), and vinylidene fluoride-chlorotrifluoroethylene-based fluororubbers (VDF-CTFE-based fluororubbers), and epoxy resins. Among these, polyimide, styrene-butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable.

[0077] The thickness of the negative electrode active material layer varies depending on the intended configuration of the secondary battery, but is preferably within the range of 0.1 to 1000 μm, for example.

[0078] [Solid electrolyte layer] In the stacked battery according to the embodiment shown in FIGS. 2 and 3, the solid electrolyte layer is interposed between the above-described positive electrode active material layer and negative electrode active material layer, and is a layer that essentially contains a solid electrolyte.

[0079] There are no particular limitations on the specific form of the solid electrolyte contained in the solid electrolyte layer, and for example, a sulfide solid electrolyte or an oxide solid electrolyte can be used.

[0080] As the sulfide solid electrolyte, the sulfide solid electrolyte used in the sulfide solid electrolyte composite and its preferred forms can be similarly employed.

[0081] Examples of oxide solid electrolytes include compounds having a NASICON structure. An example of a compound having a NASICON structure is a compound represented by the general formula Li 1+x Al x Ge 2-x Compounds (LAGP) represented by (PO4)3 (0≦x≦2), general formula Li 1+x Al x Ti 2-x (PO4)3 (0≦x≦2) (LATP) and the like. Another example of an oxide solid electrolyte is LiLaTiO (for example, Li 0.34 La 0.51 TiO3), LiPON (e.g., Li 2.9 PO 3.3 N 0.46 ), LiLaZrO (e.g., Li7La3Zr2O 12 ) etc.

[0082] In the secondary battery of this embodiment, the solid electrolyte layer preferably contains the sulfide solid electrolyte composite of this embodiment (using an insulating porous material). That is, one embodiment of the present invention is a solid electrolyte layer for an electric device that contains the sulfide solid electrolyte composite of this embodiment. This improves the hydrolysis resistance of the sulfide solid electrolyte and suppresses the generation of hydrogen sulfide. Therefore, it becomes possible to handle it even in high dew point environments where it was previously unusable. In particular, the content of the sulfide solid electrolyte composite of this embodiment in the solid electrolyte layer is preferably 90 mass % or more, more preferably 95 mass % or more, and even more preferably 98 mass % or more, based on the total amount of the solid electrolyte layer.

[0083] The solid electrolyte layer may further contain a binder in addition to the solid electrolyte. The examples and preferred embodiments described in the section on the negative electrode active material layer may also be used for the binder that can be contained in the solid electrolyte layer.

[0084] 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 800 μm or less, more preferably 700 μm or less, and even more preferably 600 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.

[0085] [Cathode active material layer] 2 and 3, the positive electrode active material layer contains a positive electrode active material. The type of the positive electrode active material is not particularly limited, but a positive electrode active material containing sulfur can be preferably used.

[0086] (Cathode active material containing sulfur) The type of sulfur-containing positive electrode active material is not particularly limited, but includes elemental sulfur (S) as well as particles or thin films of organic or inorganic sulfur compounds. Any material can be used as long as it utilizes the sulfur redox reaction to release lithium ions during charging and absorb lithium ions during discharging. Examples of organic sulfur compounds include disulfide compounds, sulfur-modified polyacrylonitriles, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), and polycarbonate, as exemplified by the compounds described in International Publication No. 2010 / 044437. Among these, disulfide compounds, sulfur-modified polyacrylonitriles, and rubeanic acid are preferred, with sulfur-modified polyacrylonitrile being particularly preferred. Disulfide compounds containing dithiobiurea derivatives, thiourea groups, thioisocyanates, or thioamide groups are more preferred. Here, sulfur-modified polyacrylonitrile is a modified polyacrylonitrile containing sulfur atoms, obtained by mixing sulfur powder and polyacrylonitrile and heating the mixture under inert gas or reduced pressure. The estimated structure is that polyacrylonitrile is ring-closed to form a polycyclic ring, and at least a part of S is bonded to C, as shown in Chem. Mater. 2011, 23, 5024-5028. The compound described in this document has a Raman spectrum of 1330 cm -1 and 1560cm -1 There is a strong peak signal near 307 cm -1 , 379cm -1 , 472cm -1 , 929cm -1There is a peak around . On the other hand, inorganic sulfur compounds are preferred due to their excellent stability, and specific examples include elemental sulfur (S), TiS2, TiS3, TiS4, NiS, NiS2, CuS, FeS2, Li2S, MoS2, MoS3, MnS, MnS2, CoS, CoS2, etc. Among them, S, S-carbon composite, TiS2, TiS3, TiS4, FeS2, and MoS2 are preferred, elemental sulfur (S), TiS2, and FeS2 are more preferred, and elemental sulfur (S) is particularly preferred from the viewpoint of high capacity. Note that, as elemental sulfur (S), α-sulfur, β-sulfur, or γ-sulfur having an S8 structure can be used.

[0087] The cathode material according to this embodiment may further include a sulfur-free cathode active material in addition to the sulfur-containing cathode active material. Examples of the sulfur-free cathode active material include layered rock salt active materials such as LiCoO2, LiMnO2, LiNiO2, LiVO2, and Li(Ni-Mn-Co)O2; LiMn2O4; and LiNi 0.5 Mn 1.5 Examples of oxide active materials include spinel-type active materials such as LiFePO4 and LiMnPO4, olivine-type active materials such as LiFeSiO4 and LiMnSiO4, and Si-containing active materials such as LiFeSiO4 and LiMnSiO4. 12 Examples include:

[0088] In some cases, two or more kinds of positive electrode active materials may be used in combination. Of course, positive electrode active materials other than those mentioned above may also be used. However, the content of the sulfur-containing positive electrode active material in 100% by mass of the total amount 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.

[0089] The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but is preferably within the range of 35 to 99 mass %, and more preferably within the range of 40 to 90 mass %, for example.

[0090] The positive electrode active material layer may further contain a conductive additive (one that does not hold a solid electrolyte inside the pores) and / or a binder, and specific and preferred forms thereof may be similar to those described in the section on the negative electrode active material layer above.

[0091] Similarly, the positive electrode active material layer preferably further includes a solid electrolyte, and particularly preferably includes a sulfide solid electrolyte. The specific and preferred forms of solid electrolytes such as sulfide solid electrolytes can be similarly adopted as those described in the negative electrode active material layer section above. Preferably, the positive electrode active material layer includes the sulfide solid electrolyte composite of this embodiment (using an electronically conductive porous material) as the solid electrolyte. This improves the hydrolysis resistance of the sulfide solid electrolyte and suppresses the generation of hydrogen sulfide. Therefore, it becomes possible to handle the positive electrode active material layer even in high dew point environments where it was previously unusable. Furthermore, the electronically conductive porous material also functions as an electron conduction path, thereby improving the electronic conductivity of the positive electrode active material layer.

[0092] The thickness of the positive electrode active material layer varies depending on the intended configuration of the secondary battery, but is preferably within the range of 0.1 to 1000 μm, for example.

[0093] [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.

[0094] [Positive and negative leads] Although not shown, the current collectors (11′, 11″) may be electrically connected to the current collector plates (25, 27) via positive and negative electrode leads. Materials used in known lithium secondary batteries may be used as the constituent materials of the positive and negative electrode leads. The parts removed from the exterior are preferably 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 products (e.g., automobile parts, particularly electronic devices).

[0095] [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 2 and 3 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.

[0096] 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.

[0097] Although one embodiment of a lithium secondary battery has been described above, the present invention is not limited to the configuration described in the above embodiment, and can be modified as appropriate based on the claims.

[0098] For example, the type of battery to which the lithium secondary battery according to the present invention 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.

[0099] Furthermore, the secondary battery according to this embodiment does not have to be an all-solid-state type. 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).

[0100] The liquid electrolyte (electrolytic solution) that can be used has a form in which a lithium salt is dissolved in an organic solvent. Examples of the organic solvent that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propionate (MP), methyl acetate (MA), methyl formate (MF), 4-methyldioxolane (4MeDOL), dioxolane (DOL), 2-methyltetrahydrofuran (2MeTHF), tetrahydrofuran (THF), dimethoxyethane (DME), propylene carbonate (PC), butylene carbonate (BC), dimethyl sulfoxide (DMSO), and γ-butyrolactone (GBL). Among these, from the viewpoint of further improving the rapid charging characteristics and output characteristics, the organic solvent is preferably a chain carbonate, more preferably at least one selected from the group consisting of diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC), and more preferably selected from ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC).

[0101] Examples of lithium salts include Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), Li(C2F5SO2)2N, LiPF6, LiBF4, LiClO4, LiAsF6, and LiCF3SO3. Among these, the lithium salt is preferably Li(FSO2)2N (LiFSI) from the viewpoints of battery output and charge / discharge cycle characteristics.

[0102] The liquid electrolyte (electrolytic solution) may further contain additives other than the above-mentioned components. Specific examples of such compounds include ethylene carbonate, vinylene carbonate, methyl vinylene carbonate, dimethyl vinylene carbonate, phenyl vinylene carbonate, diphenyl vinylene carbonate, ethyl vinylene carbonate, diethyl vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate, 1-methyl-1-vinyl ethylene carbonate, 1-methyl-2-vinyl ethylene carbonate, 1-ethyl-1-vinyl ethylene carbonate, and 1-ethyl-2-vinyl ethylene carbonate. Examples of the additive include ethylene carbonate, vinyl vinylene carbonate, allyl ethylene carbonate, vinyloxymethyl ethylene carbonate, allyloxymethyl ethylene carbonate, acryloxymethyl ethylene carbonate, methacryloxymethyl ethylene carbonate, ethynyl ethylene carbonate, propargyl ethylene carbonate, ethynyloxymethyl ethylene carbonate, propargyloxyethylene carbonate, methylene ethylene carbonate, and 1,1-dimethyl-2-methylene ethylene carbonate. These additives may be used alone or in combination of two or more. The amount of additive used in the electrolyte solution can be adjusted as appropriate.

[0103] [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.

[0104] 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.

[0105] [vehicle] A battery or a battery pack consisting of a combination of multiple batteries can be mounted on a vehicle. The present invention makes it possible to construct a long-life battery with excellent long-term reliability, and by mounting such a battery, it is possible to construct a plug-in hybrid electric vehicle with a long EV driving range or an electric vehicle with a long driving range per charge. The battery or battery pack can be used in, for example, 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 use 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.

[0106] In the above embodiment, a lithium secondary battery has been described as an example of an electric device, but the sulfide solid electrolyte composite of the present embodiment is not limited thereto and can be applied to other types of secondary batteries and even primary batteries. Furthermore, the sulfide solid electrolyte composite can be applied not only to batteries but also to electric devices such as electric double layer capacitors, hybrid capacitors, and lithium ion capacitors. [Example]

[0107] 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.

[0108] [Example 1] (Preparation of sulfide solid electrolyte composite) In a glove box with an argon atmosphere and a dew point of -68°C or less, 1.00 g of sulfide solid electrolyte (LiPSCl (LPSCl) manufactured by Ampcera) was added to 15 mL of ultra-dehydrated ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to dissolve the sulfide solid electrolyte in ethanol. The resulting sulfide solid electrolyte ethanol solution was mixed with a porous carbon material (Knobel® MJ(4)030 manufactured by Toyo Tanso Co., Ltd., average pore diameter: 30 nm, total pore volume: 2.0 cm). 3 0.20 g of sulfide solid electrolyte solution was added and stirred thoroughly to impregnate the carbon. The container containing the carbon impregnated with the sulfide solid electrolyte solution was connected to a vacuum device, and the container was reduced in pressure to 1 Pa or less using an oil rotary pump. The solvent, ethanol, volatilizes under reduced pressure, so the ethanol was removed. After the ethanol was removed under reduced pressure, the container was heated to 180°C under reduced pressure and heat-treated for 3 hours to obtain a sulfide solid electrolyte composite.

[0109] Regarding the sulfide solid electrolyte composite prepared in this example, it was confirmed by TEM-EDX that the sulfide solid electrolyte was disposed inside the pores of the porous material.

[0110] Specifically, in order to avoid thermal deterioration of the sulfide solid electrolyte component, powder particles of the sulfide solid electrolyte composite were fragmented to a thickness of about 100 nm using a cryoplasma focused ion beam processing apparatus (Helios G4 PFIB CXe manufactured by Thermo Scientific, acceleration voltage: 30 kV) that utilizes a cryogenic state. The fragmented observation sample was transported into a TEM apparatus (JEM-F200, a multifunctional analytical transmission electron microscope manufactured by JEOL, acceleration voltage: 200 kV) without exposure to air, and while confirming the microstructure, elemental mapping data of the portion corresponding to the inside of the particles was obtained using an EDX apparatus (energy dispersive X-ray spectroscopic analyzer, Dual SDD manufactured by JEOL, acceleration voltage: 200 kV) attached to the TEM (characteristic X-ray measurement energy band for EDX mapping: 0 - 5 keV). From the obtained elemental mapping data, it was confirmed that the sulfide solid electrolyte is disposed inside the pores of the porous material. In this example, P (phosphorus) or S (sulfur), which is an element contained only in the sulfide solid electrolyte and not in the porous material or other materials, was used as a labeling element to determine whether the pores of the porous material were filled with the sulfide solid electrolyte.

[0111] Also, from the charged mass of the porous material and the sulfide solid electrolyte, the specific gravity of the sulfide solid electrolyte, and the total pore volume of the porous material, the volume V p of the sulfide solid electrolyte with respect to the volume V el of the pores of the porous material (V el / V p ) was determined, and it was confirmed that V el / V p was 0.8 or more. Here, the measurement of the total pore volume was performed by nitrogen adsorption / desorption measurement. Specifically, it was performed using BELSORP mini manufactured by MicrotracBEL Corporation, at a temperature of -196°C, by the multipoint method. An adsorption isotherm in the relative pressure range of 0.01 < P / P0 < 0.05 was obtained, and the total pore volume was determined from the volume of adsorbed N2 at a relative pressure of 0.96.

[0112] [Example 2] In a glove box with an argon atmosphere at a dew point of -68°C or less, 1.00 g of sulfide solid electrolyte (Li6PS5Cl, manufactured by Ampcera) was added to 15 mL of ultra-dehydrated ethanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to dissolve the sulfide solid electrolyte in ethanol. The obtained sulfide solid electrolyte ethanol solution was mixed with a porous material, titania (titania monolith manufactured by SNG Corporation, average through pore diameter: 1 μm, average pore diameter: 11 nm, total pore volume: 0.50 cm). 3 After impregnation, 0.20 g of sulfide-based solid electrolyte composite was added and impregnated, and the pressure in the vessel was reduced to 1 Pa or less using an oil rotary pump to remove the ethanol. After the ethanol was removed under reduced pressure, the vessel was heated to 350°C under reduced pressure and subjected to heat treatment for 3 hours to obtain a sulfide-based solid electrolyte composite.

[0113] Regarding the sulfide solid electrolyte composite prepared in this example, it was confirmed by TEM-EDX in the same manner as above that the sulfide solid electrolyte was disposed inside the pores of the porous material. el / V p was confirmed to be 0.8 or higher.

[0114] [Example 3] A sulfide solid electrolyte composite was produced in the same manner as in Example 1, except that the sulfide solid electrolyte was changed to 75Li2S-25P2S5 (LPS) manufactured by Ampcera and the solvent was changed to ultra-dehydrated acetonitrile (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.).

[0115] Regarding the sulfide solid electrolyte composite prepared in this example, it was confirmed by TEM-EDX in the same manner as above that the sulfide solid electrolyte was disposed inside the pores of the porous material. el / V p was confirmed to be 0.8 or higher.

[0116] [Comparative Example 1] Li2S was used as is.

[0117] Comparative Example 2 A sulfide solid electrolyte, Li6PS5Cl (LPSCl) manufactured by Ampcera, was used as is.

[0118] Comparative Example 3 Ampcera's Li6PS5Cl sulfide solid electrolyte 0.5 Br 0.5 (LPSClBr) was used as is.

[0119] Comparative Example 4 The sulfide solid electrolyte, 75Li2S-25P2S5 (LPS) manufactured by Ampcera, was used as is.

[0120] Comparative Example 5 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, LPS, and PO (manufactured by Aldrich) were weighed out to a total weight of 0.20 g in a molar ratio of 8:2 (LPS:PO), placed in a 45 mL zirconia container, and processed in a planetary ball mill (manufactured by Fritsch, Premium line P-7) at 420 rpm for 4 hours to obtain a sulfide solid electrolyte (LPSO).

[0121] Comparative Example 6 In a glove box with an argon atmosphere and a dew point of −68°C or lower, 40 g of 5 mm diameter zirconia balls, LPS, and LiN (manufactured by Aldrich) were weighed out to a total weight of 0.20 g in a molar ratio of 8:2 (LPS:LiN). These were placed in a 45 mL zirconia container and milled at 420 rpm for 4 hours in a planetary ball mill (manufactured by Fritsch, Premium line P-7) to obtain a sulfide solid electrolyte (LiN-LPS).

[0122] Comparative Example 7 In a glove box with an argon atmosphere and a dew point of −68°C or lower, 0.250 g of a sulfide solid electrolyte (Li6PS5Cl, manufactured by Ampcera) and 0.050 g of carbon (Knobel® MJ(4)030, manufactured by Toyo Tanso Co., Ltd.) were placed in a 45 mL zirconia container and treated at 370 rpm for 4 hours in a planetary ball mill (Premium line P-7, manufactured by Fritsch) to obtain a composite.

[0123] Furthermore, elemental map data was obtained for the composite prepared in this comparative example using TEM-EDX in the same manner as described above, and it was found that the sulfide solid electrolyte was not disposed inside the pores of the porous material.

[0124] <<Measurement of hydrogen sulfide generation amount>> The amount of hydrogen sulfide generated in a humidified environment was measured for the sulfide solid electrolyte composites prepared in each of the above examples and the solid electrolyte or composite samples of each of the comparative examples using an apparatus such as that shown in Figure 4. A desiccator equipped with a hydrogen sulfide sensor, a temperature sensor, and a humidity sensor was prepared in a glove box filled with argon gas, and 20 mg of sample was placed in the desiccator. Humidified air, whose relative humidity was controlled by mixing dry air with humidified air obtained by passing dry air through a water bubbling unit at a controlled flow rate, was introduced into the glove box at a predetermined flow rate. For each sample, the amount of hydrogen sulfide generated per unit mass of the sulfide solid electrolyte (excluding the porous material) was measured after 30 minutes under conditions of 25°C and 65% RH. The results are shown in Table 1 below. In Table 1, the amount of hydrogen sulfide generated is shown as a relative value to the amount of hydrogen sulfide generated in Comparative Example 1.

[0125] <<Measurement of ionic conductivity>> The lithium ion conductivity was measured for the sulfide solid electrolyte composites prepared in the above examples and the solid electrolyte or composite samples of each comparative example. Specifically, LPSCl powder / sulfide solid electrolyte composite / LPSCl powder was press-molded at a pressure of 350 MPa to prepare electron-blocking sulfide solid electrolyte composite pellets. The lithium ion conductivity (25°C) of these sulfide solid electrolyte composite pellets was measured by an AC impedance method while they were pressurized at 100 MPa. A frequency response analyzer (FRA) was used for the measurement, and the measurement conditions were an amplitude voltage of 10 mV and a measurement frequency range of 7 MHz to 1 Hz. The results are shown in Table 1 below.

[0126] [Table 1]

[0127] The results shown in Table 1 indicate that the sulfide solid electrolyte composites of Examples 1 to 3, which support the sulfide solid electrolyte inside the pores of the porous material, can significantly improve the hydrolysis resistance of the sulfide solid electrolyte without significantly impairing the ionic conductivity of the sulfide solid electrolyte. For example, the sulfide solid electrolyte composites of Examples 1 to 3 generate less than one-tenth the amount of hydrogen sulfide compared to Li2S in Comparative Example 1. On the other hand, as shown in Comparative Examples 1 to 6, it is difficult to achieve sufficient hydrolysis resistance by simply improving the sulfide solid electrolyte material. Furthermore, it was found that the method of mechanically mixing the porous material and the sulfide solid electrolyte, as in Comparative Example 7, fails to introduce the sulfide solid electrolyte into the pores of the porous material, resulting in reduced hydrolysis resistance. [Explanation of symbols]

[0128] 10a stacked 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 cell layer, 21 power generation elements, 25 negative current collector plate, 27 positive current collector plate, 29 Laminating film, 100 Sulfide solid electrolyte complex, 110 porous materials, 110a pores, 130 Sulfide solid electrolyte, 140 Contact interface.

Claims

1. a porous material having pores; a sulfide solid electrolyte supported inside the pores; and Including, A solid electrolyte layer for an electric device, comprising a sulfide solid electrolyte composite, wherein the pores have an average pore size of 1 μm or less and the pore volume fraction of the porous material is 30 to 95%.

2. A porous material having pores; a sulfide solid electrolyte supported inside the pores; and Including, The total pore volume of the porous material is 0.50 cm ３ A solid electrolyte layer for an electrical device, comprising a sulfide solid electrolyte composite having a SiO 2 content of SiO 2 / g or more.

3. A porous material having pores; a sulfide solid electrolyte supported inside the pores; and Including, A solid electrolyte layer for an electrical device, comprising a sulfide solid electrolyte composite, wherein the ratio of the volume of the sulfide solid electrolyte to the volume of the pores of the porous material is 0.8 or more.

4. The solid electrolyte layer for an electrical device according to claim 1, wherein the pores are filled with only the sulfide solid electrolyte.

5. 5. The solid electrolyte layer for an electrical device according to claim 1, wherein the porous material is a carbon material.

6. 5. The solid electrolyte layer for an electrical device according to claim 1, wherein the porous material is a metal oxide material.

7. 7. The solid electrolyte layer for an electrical device according to claim 1, wherein the sulfide solid electrolyte contains an alkali metal atom and a phosphorus atom and / or a boron atom.

8. 8. The solid electrolyte layer for an electrical device according to claim 7, wherein the alkali metal atoms are lithium atoms.

9. An electric device comprising the solid electrolyte layer for an electric device according to any one of claims 1 to 8.

10. 10. The electrical device of claim 9, which is a secondary battery.

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