Composite solid electrolyte, all-solid-state battery, method for producing composite solid electrolyte, and method for producing all-solid-state battery

Abstract

To provide a composite solid electrolyte capable of suppressing a decrease in Coulomb efficiency in a charge / discharge cycle of an all-solid-state battery, and a manufacturing method thereof.SOLUTION: A composite solid electrolyte includes a sulfide solid electrolyte and an additive. The additive is a sulfur-based cyclic compound having an S=O bond, lithium nitrate, or a combination thereof. The content ratio of the additive is preferably 5 mass% or more and 20 mass% or less, and more preferably the sulfur-based cyclic compound is a cyclic sulfonic acid ester. A manufacturing method of the composite solid electrolyte includes mixing a sulfide solid electrolyte and an additive to prepare a composite solid electrolyte, and the additive is a sulfur-based cyclic compound having an S=O bond, lithium nitrate, or a combination thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a composite solid electrolyte, an all-solid-state battery, a method for producing a composite solid electrolyte, and a method for producing an all-solid-state battery. [Background technology]

[0002] Due to their high energy density, non-aqueous electrolyte secondary batteries, typified by lithium ion non-aqueous electrolyte secondary batteries, are widely used in electronic devices such as personal computers and communication terminals, automobiles, etc. The non-aqueous electrolyte secondary batteries generally include an electrode assembly having a pair of electrically isolated electrodes and a non-aqueous electrolyte interposed between the electrodes, and are configured to charge and discharge by transferring ions between the electrodes.

[0003] In recent years, with the aim of improving the safety of non-aqueous electrolyte secondary batteries, all-solid-state batteries have been proposed that use a sulfide solid electrolyte or the like as the non-aqueous electrolyte instead of a liquid electrolyte containing an organic solvent or the like (see Patent Document 1).

[0004] As sulfide solid electrolytes, 70Li2S·30P2S5 glass ceramics and 60Li2S·25P2S5·10Li3N glass ceramics are used. -3 It has been reported that they exhibit high ionic conductivity of over 100 S / cm (Solid State Ionics, 177, 2721 (2006), Solid State Ionics, 304, 85 (2016)).

[0005] However, when the relationship between applied pressure and cycle performance was evaluated using an all-solid-state Li-Si half-cell with a Si:Cu:sulfide solid electrolyte (77.5Li2S 22.5P2S5) composition of 1:1:5 (m / m / m), it was reported that the Coulombic efficiency was low even when a high pressure (230 MPa) was applied, which was not enough to cause silicon isolation (Journal of the Electrochemical Society, 160, 1, A77 (2013)). Furthermore, first-principles calculations revealed that sulfide solid electrolytes inherently have low oxidation resistance and low reduction resistance (ACS Appl. Mater. Interfaces, 7, 23685 (2015)). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-340257 Summary of the Invention [Problem to be solved by the invention]

[0007] In energy storage devices such as nonaqueous electrolyte secondary batteries used in hybrid electric vehicles (hereinafter also referred to as "HEVs") and hybrid industrial machinery (heavy machinery, construction machinery, etc.), it is required to suppress the decrease in Coulomb efficiency during charge / discharge cycles, and it is also desired to further suppress the decrease in Coulomb efficiency in all-solid-state batteries.

[0008] The present invention has been made in light of the above circumstances, and has an object to provide a composite solid electrolyte that can suppress a decrease in coulombic efficiency during charge-discharge cycles of an all-solid-state battery. [Means for solving the problem]

[0009] One aspect of the present invention, which has been made to solve the above-mentioned problems, is a composite solid electrolyte including a sulfide solid electrolyte and an additive, wherein the additive is a sulfur-based cyclic compound having an S═O bond, lithium nitrate, or a combination thereof.

[0010] Another aspect of the present invention is a method for producing a composite solid electrolyte, comprising mixing a sulfide solid electrolyte with an additive to produce a composite solid electrolyte, wherein the additive is a sulfur-based cyclic compound having an S═O bond, lithium nitrate, or a combination thereof. [Effects of the Invention]

[0011] A composite solid electrolyte according to one aspect of the present invention can suppress a decrease in coulombic efficiency during charge-discharge cycles of an all-solid-state battery. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery according to one embodiment of the present invention. [Figure 2] FIG. 2 is a graph showing the relationship between the number of charge / discharge cycles and the coulombic efficiency for the examples and the reference example. DETAILED DESCRIPTION OF THE INVENTION

[0013] One aspect of the present invention is a composite solid electrolyte comprising a sulfide solid electrolyte and an additive, wherein the additive is a sulfur-based cyclic compound having an S═O bond, lithium nitrate, or a combination thereof.

[0014] The present inventors believed that improving the reduction resistance of the sulfide solid electrolyte was necessary to improve the effect of suppressing a decrease in Coulombic efficiency during the charge-discharge cycles of an all-solid-state battery, and as a result of their investigations, they found that reduction resistance could be imparted to the sulfide solid electrolyte by using a specific additive. They then believed that combining a specific additive with a sulfide solid electrolyte could increase the reduction resistance of the solid electrolyte and suppress a decrease in Coulombic efficiency during the charge-discharge cycles of an all-solid-state battery, leading to the present invention.

[0015] This composite solid electrolyte contains a sulfide solid electrolyte and an additive, and the additive is a sulfur-based cyclic compound having an S=O bond, lithium nitrate, or a combination thereof, which can suppress a decrease in Coulombic efficiency during the charge-discharge cycles of an all-solid-state battery. While the reason for this is unclear, the following is presumed. Typical sulfide solid electrolytes are known to be susceptible to reductive decomposition and exhibit large reductive decomposition capacities. This composite solid electrolyte is formed by combining the sulfur-based cyclic compound having an S=O bond with a sulfide solid electrolyte and using it as the solid electrolyte for the anode or the electrolyte layer interposed between the anode and cathode. It is believed that the sulfur-based cyclic compound having an S=O bond undergoes ring-opening upon reduction to form electronically insulating LiS and LiO. This results in the formation of an ultrathin, electronically insulating coating on the surface of the anode or electrolyte layer, which is presumed to suppress continuous reductive decomposition of the sulfide solid electrolyte and improve the Coulombic efficiency. The reductive decomposition potential of nonaqueous electrolytes used in typical lithium-ion nonaqueous electrolyte secondary batteries is less than 1.0 V (e.g., ethylene carbonate is approximately 0.6 V). Therefore, when 1,3-propene sultone, a sulfur-based cyclic compound having an S=O bond, is used as an additive in a lithium-ion nonaqueous electrolyte secondary battery, the 1,3-propene sultone decomposes before the other components of the nonaqueous electrolyte, forming a coating on the surface of the negative electrode, which is thought to suppress decomposition of the nonaqueous electrolyte. In contrast, the sulfide solid electrolyte has a higher reductive decomposition potential than 1,3-propene sultone, and therefore, it is thought that the effects of this composite solid electrolyte are achieved through a mechanism different from that of the nonaqueous electrolyte in lithium-ion nonaqueous electrolyte secondary batteries. On the other hand, this composite solid electrolyte is formed by combining lithium nitrate, which has a higher reduction potential than the sulfide solid electrolyte, with the sulfide solid electrolyte and using it as the solid electrolyte in the negative electrode or in the electrolyte layer interposed between the negative electrode and the positive electrode. As a result, the lithium nitrate is reductively decomposed before the sulfide solid electrolyte. As a result, a thin electronically insulating coating (SEI: Solid Electrolyte Interphase) is formed on the surface of the negative electrode due to the reductive decomposition of lithium nitrate. Therefore, this composite solid electrolyte can suppress the continuous reductive decomposition of the solid electrolyte that occurs on the negative electrode side and can suppress the decrease in Coulombic efficiency during charge-discharge cycles. Here, the "SEI" refers to a coating that forms on the negative electrode surface due to the reductive decomposition of the electrolyte during the first charge. This coating functions as a passivation that suppresses subsequent reductive decomposition of the electrolyte, and at the same time, it provides a site for lithium ion insertion and desorption at the interface between the negative electrode and the electrolyte through lithium ion conduction.

[0016] The content of the additive in the composite solid electrolyte is preferably 5% by mass or more and 20% by mass or less, which further improves the reduction resistance of the composite solid electrolyte and further enhances the effect of suppressing the decrease in coulomb efficiency during the charge-discharge cycle of the all-solid-state battery.

[0017] The sulfur-based cyclic compound is preferably a cyclic sulfonate ester, which further improves the reduction resistance of the composite solid electrolyte and further enhances the effect of suppressing the decrease in coulomb efficiency during charge-discharge cycles of the all-solid-state battery.

[0018] An all-solid-state battery according to another aspect of the present invention includes a negative electrode, a positive electrode, and an electrolyte layer interposed between the negative electrode and the positive electrode, wherein the negative electrode, the electrolyte layer, or a combination thereof contains the composite solid electrolyte. In the all-solid-state battery, the negative electrode, the electrolyte layer, or a combination thereof contains the composite solid electrolyte, so that the additive is reductively decomposed before the sulfide solid electrolyte. As a result, an electronically insulating coating is formed on the negative electrode side by reductive decomposition of the additive, which suppresses continuous reductive decomposition of the sulfide solid electrolyte on the negative electrode side and is highly effective in suppressing a decrease in coulombic efficiency during charge-discharge cycles.

[0019] A method for producing a composite solid electrolyte according to another aspect of the present invention includes mixing a sulfide solid electrolyte with an additive to produce a composite solid electrolyte, wherein the additive is a sulfur-based cyclic compound having an S═O bond, lithium nitrate, or a combination thereof.

[0020] The method for producing the composite solid electrolyte includes mixing a sulfide solid electrolyte with an additive to produce a composite solid electrolyte, and the additive is a sulfur-based cyclic compound having an S=O bond, lithium nitrate, or a combination thereof, so that the composite solid electrolyte produced has reduction resistance and an excellent effect of suppressing a decrease in coulombic efficiency during the charge-discharge cycle of an all-solid-state battery.

[0021] In the method for producing the composite solid electrolyte, the content of the additive in the composite solid electrolyte is preferably 5% by mass or more and 20% by mass or less. By having the content of the additive in the composite solid electrolyte be 5% by mass or more and 20% by mass or less, it is possible to produce a composite solid electrolyte that has improved reduction resistance and is more effective in suppressing a decrease in coulomb efficiency during charge-discharge cycles of an all-solid-state battery.

[0022] A method for producing an all-solid-state battery according to another aspect of the present invention includes fabricating at least one of an anode and an electrolyte layer using the composite solid electrolyte or a composite solid electrolyte obtained by the method for producing the composite solid electrolyte. Because the method for producing an all-solid-state battery includes fabricating at least one of an anode and an electrolyte layer using the composite solid electrolyte or a composite solid electrolyte obtained by the method for producing the composite solid electrolyte, it is possible to produce an all-solid-state battery that is excellent in suppressing a decrease in coulombic efficiency during charge-discharge cycles.

[0023] Hereinafter, embodiments of the composite solid electrolyte, the all-solid-state battery, the method for manufacturing the composite solid electrolyte, and the method for manufacturing the all-solid-state battery according to the present invention will be described in detail.

[0024] <Composite solid electrolyte> The composite solid electrolyte includes a sulfide solid electrolyte and an additive, wherein the additive is a sulfur-based cyclic compound having an S=O bond, lithium nitrate, or a combination thereof. The composite solid electrolyte includes a sulfide solid electrolyte and an additive, wherein the additive is a sulfur-based cyclic compound having an S=O bond, lithium nitrate, or a combination thereof, and therefore has excellent reduction resistance and can suppress a decrease in coulombic efficiency during charge-discharge cycles of an all-solid-state battery. The composite solid electrolyte can be used in any application requiring ionic conductivity. In particular, the composite solid electrolyte is preferably used in a lithium all-solid-state battery.

[0025] The sulfide solid electrolyte preferably has high lithium ion conductivity, and examples thereof include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-P2S5-Li3N, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S 2n (where m and n are positive numbers, and Z is Ge, Zn, or Ga.), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers, and M is P, Si, Ge, B, Al, Ga, or In.) Li 10 GeP2S 12 Among these, Li2S-P2S5 is preferred, and xLi2S·(100-x)P2S5 (70≦x≦80) is more preferred from the viewpoint of good lithium ion conductivity.

[0026] The additive is a sulfur-based cyclic compound having an S=O bond, lithium nitrate, or a combination thereof. It is believed that the sulfur-based cyclic compound having an S=O bond used as an additive in the composite solid electrolyte undergoes ring-opening upon reduction to form electronically insulating Li2S and Li2O. This is believed to result in the formation of an ultrathin electronically insulating coating on the surface of the negative electrode or electrolyte layer. Meanwhile, the composite solid electrolyte uses lithium nitrate, which has a higher reduction potential than the sulfide solid electrolyte, as an additive, so that lithium nitrate is reductively decomposed before the sulfide solid electrolyte. As a result, an SEI is formed on the surface of the negative electrode or electrolyte layer. In this way, the composite solid electrolyte can suppress the continuous reductive decomposition of the sulfide solid electrolyte on the negative electrode side and also suppress a decrease in coulombic efficiency during charge-discharge cycles.

[0027] Examples of the sulfur-based cyclic compound having an S═O bond include sultone compounds, cyclic sulfate compounds, cyclic sulfite compounds, sulfolane compounds, cyclic disulfonate compounds, and sulfobenzoic anhydride.

[0028] Examples of the sultone compound include 1,3-propane sultone, 1,3-propene sultone, 2,4-butane sultone, and 1,4-butane sultone.

[0029] Examples of the cyclic sulfite compound include ethylene sulfite, 1,2-propylene glycol sulfite, trimethylene sulfite, and 1,3-butylene glycol sulfite.

[0030] Examples of sulfolane compounds include sulfolane, 3-sulfolene, 1,1-dioxothiophene, 3-methylsulfolane, 3-methyl-2,5-dihydrothiophene-1,1-dioxide, and methyl 3-sulfolene-3-carboxylate.

[0031] Examples of the cyclic disulfonate compounds include methylene-methane disulfonate esters and ethylene-methane disulfonate esters.

[0032] The sulfur-based cyclic compound is preferably a cyclic sulfonate ester, which further improves the reduction resistance of the composite solid electrolyte and further enhances the effect of suppressing the decrease in coulomb efficiency during charge-discharge cycles of the all-solid-state battery.

[0033] The lower limit of the content of the additive in the composite solid electrolyte is preferably 1% by mass, more preferably 3% by mass, and even more preferably 5% by mass. Meanwhile, the upper limit of the content of the additive is preferably 20% by mass, more preferably 18% by mass, and even more preferably 15% by mass. By having the content of the additive in the above range, the reduction resistance of the composite solid electrolyte is further improved, and the effect of suppressing the decrease in Coulomb efficiency during the charge-discharge cycle of the all-solid-state battery can be further enhanced. The preferred range of the content of the additive in the composite solid electrolyte is higher than the content of the additive in a lithium ion nonaqueous electrolyte secondary battery. This is because, even if the additive is consumed at the negative electrode-nonaqueous electrolyte interface in a lithium ion nonaqueous electrolyte secondary battery, the additive is supplied to the negative electrode-nonaqueous electrolyte interface by diffusion from the bulk, so that the effect can be obtained even with a low content of the additive. On the other hand, in all-solid-state batteries, particulate additives are present in a dispersed state in the solid electrolyte, making it difficult for the above-mentioned state to occur as in the nonaqueous lithium-ion electrolyte secondary battery. As a result, it is presumed that the effect is difficult to obtain when the additive content is in a low range as in the case of the nonaqueous lithium-ion electrolyte secondary battery.

[0034] The lower limit of the ionic conductivity of the composite solid electrolyte at 25°C is 1.0 × 10 -5 S / cm is preferred, 5.0×10 -5 S / cm is more preferable, and 1.0×10 -4 When the ionic conductivity of the composite solid electrolyte at 25°C is within the above range, the high-rate charge / discharge performance of the all-solid-state battery can be improved.

[0035] The composite solid electrolyte can be suitably used as a solid electrolyte for the negative electrode and a solid electrolyte for the electrolyte layer of an all-solid-state battery.

[0036] <All-solid-state battery> The all-solid-state battery includes a negative electrode, a positive electrode, and an electrolyte layer interposed between the negative electrode and the positive electrode. FIG. 1 is a schematic cross-sectional view showing an all-solid-state battery 10 according to one embodiment of the present invention. The all-solid-state battery 10, which is a secondary battery, includes a negative electrode 1 and a positive electrode 2 arranged with a solid electrolyte layer 3 interposed therebetween. The negative electrode 1 includes a negative electrode substrate 4 and a negative electrode mixture layer 5, with the negative electrode substrate 4 being the outermost layer of the negative electrode 1. The positive electrode 2 includes a positive electrode substrate 7 and a positive electrode mixture layer 6, with the positive electrode substrate 7 being the outermost layer of the positive electrode 2. In the all-solid-state battery 10 shown in FIG. 1, the positive electrode mixture layer 6, the solid electrolyte layer 3, the negative electrode mixture layer 5, and the negative electrode substrate 4 are stacked in this order on the positive electrode substrate 7.

[0037] In the all-solid-state battery, the negative electrode 1, the solid electrolyte layer 3, or a combination thereof contains the composite solid electrolyte. Because the negative electrode 1, the solid electrolyte layer 3, or a combination thereof contains the composite solid electrolyte, the all-solid-state battery has an excellent effect of suppressing a decrease in coulomb efficiency during charge-discharge cycles.

[0038] The all-solid-state battery may also use a solid electrolyte other than the composite solid electrolyte, which may be a sulfide solid electrolyte other than the composite solid electrolyte, an oxide-based solid electrolyte, a dry polymer electrolyte, a gel polymer electrolyte, or a quasi-solid electrolyte.

[0039] As the sulfide solid electrolyte other than the composite solid electrolyte, the above-mentioned sulfide solid electrolytes can be used.

[0040] [Negative electrode] The negative electrode 1 includes a negative electrode substrate 4 and a negative electrode mixture layer 5 laminated on the surface of the negative electrode substrate 4. The negative electrode 1 may have an intermediate layer (not shown) between the negative electrode substrate 4 and the negative electrode mixture layer 5.

[0041] (negative electrode substrate) The negative electrode substrate 4 is a layer having electrical conductivity. The material of the negative electrode substrate 4 is not limited as long as it is an electrical conductor. For example, the material may be one or more metals selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, gold, silver, iron, platinum, chromium, tin, indium, alloys containing one or more of these metals, and stainless steel alloys.

[0042] The lower limit of the average thickness of the negative electrode substrate 4 is preferably 3 μm, more preferably 5 μm, and even more preferably 8 μm. The upper limit of the average thickness of the negative electrode substrate 4 is preferably 200 μm, more preferably 100 μm, and even more preferably 50 μm. By setting the average thickness of the negative electrode substrate 4 to the above lower limit or more, the strength of the negative electrode substrate 4 can be sufficiently increased, and the negative electrode 1 can be formed well. By setting the average thickness of the negative electrode substrate 4 to the above upper limit or less, the volume of the other components can be sufficiently secured.

[0043] (Negative electrode mixture layer) The negative electrode mixture layer 5 can be formed from a so-called negative electrode mixture containing a negative electrode active material. The negative electrode mixture may contain a mixture or composite containing a negative electrode active material and a solid electrolyte. The solid electrolyte may be the composite solid electrolyte. The negative electrode mixture may also contain the composite solid electrolyte that does not form a mixture or composite with the negative electrode active material. The negative electrode mixture may contain optional components such as a solid electrolyte other than the composite solid electrolyte, a conductive agent, a binder, a filler, etc., as necessary.

[0044] <Negative electrode active material> The negative electrode active material can be appropriately selected from known negative electrode active materials. A material capable of absorbing and releasing lithium ions is usually used as the negative electrode active material for lithium ion secondary batteries. Examples of the negative electrode active material include metallic Li; metals or semimetals such as Si and Sn; metal oxides or semimetal oxides such as Si oxide, Ti oxide, and Sn oxide; and Li4Ti5O 12 , LiTiO 2、Examples of the material include titanium-containing oxides such as TiNbO; polyphosphate compounds; silicon carbide; and carbon materials such as graphite and non-graphitic carbon (easily graphitizable carbon or non-graphitizable carbon). Among these materials, graphite and non-graphitic carbon are preferred. In the negative electrode active material layer, one of these materials may be used alone, or two or more may be used in combination.

[0045] "Graphite" refers to graphite that has an average lattice spacing (d 002 ) is 0.33 nm or more and less than 0.34 nm. Examples of graphite include natural graphite and artificial graphite. Artificial graphite is preferred from the viewpoint of being able to obtain a material with stable physical properties.

[0046] "Non-graphitic carbon" refers to the carbon that has an average lattice spacing (d 002 ) is 0.34 nm or more and 0.42 nm or less. Non-graphitic carbon includes non-graphitizable carbon and graphitizable carbon. Examples of non-graphitic carbon include resin-derived materials, petroleum pitch or petroleum pitch-derived materials, petroleum coke or petroleum coke-derived materials, plant-derived materials, and alcohol-derived materials.

[0047] Here, the "discharged state" refers to a state in which an open circuit voltage is 0.7 V or higher in a single-electrode battery using a negative electrode containing a carbon material as the negative electrode active material as a working electrode and metallic Li as a counter electrode. Since the potential of the metallic Li counter electrode in the open circuit state is approximately equal to the redox potential of Li, the open circuit voltage in the single-electrode battery is approximately equal to the potential of the negative electrode containing the carbon material relative to the redox potential of Li. In other words, an open circuit voltage of 0.7 V or higher in the single-electrode battery means that lithium ions capable of being absorbed and released during charging and discharging have been sufficiently released from the carbon material, which is the negative electrode active material.

[0048] "Non-graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.36 nm or more and 0.42 nm or less.

[0049] "Graphitizable carbon" means the above d 002 This refers to carbon materials with a particle size of 0.34 nm or more and less than 0.36 nm.

[0050] The lower limit of the content of the negative electrode active material in the negative electrode mixture is preferably 10% by mass, more preferably 15% by mass. The upper limit of the content of the negative electrode active material is preferably 60% by mass, more preferably 70% by mass, even more preferably 80% by mass, even more preferably 90% by mass, and particularly preferably 95% by mass. By setting the content of the negative electrode active material within the above range, the electrical capacity of the all-solid-state battery can be increased.

[0051] <Mixture or Complex> The mixture is a mixture prepared by mixing the negative electrode active material and the composite solid electrolyte by mechanical milling, etc. For example, the mixture of the negative electrode active material and the composite solid electrolyte can be obtained by mixing particulate negative electrode active material and particulate composite solid electrolyte. Examples of the composite include a composite in which the negative electrode active material and the composite solid electrolyte are chemically or physically bonded, a composite in which the negative electrode active material and the composite solid electrolyte are mechanically combined, etc. The composite is one in which the negative electrode active material and the composite solid electrolyte exist within a single particle, and examples of the composite include one in which the negative electrode active material and the composite solid electrolyte form an aggregated state, and one in which the composite solid electrolyte-containing coating is formed on at least a portion of the surface of the negative electrode active material. The mixture or composite may contain a solid electrolyte other than the composite solid electrolyte. When the negative electrode active material contained in the negative electrode mixture and the composite solid electrolyte form a mixture or a composite, the reduction resistance of the composite solid electrolyte can be improved while maintaining high ionic conductivity, and therefore, the effect of suppressing a decrease in coulombic efficiency during charge-discharge cycles is excellent.

[0052] When the negative electrode mixture contains the composite solid electrolyte, the lower limit of the content of the composite solid electrolyte in the negative electrode mixture may be 5 mass%, preferably 10 mass%. The upper limit of the content of the composite solid electrolyte in the negative electrode mixture is preferably 90 mass%, more preferably 85 mass%, even more preferably 80 mass%, and particularly preferably 75 mass%. By setting the content of the composite solid electrolyte in the negative electrode mixture within the above range, the effect of suppressing a decrease in Coulomb efficiency during charge-discharge cycles of an all-solid-state battery can be further improved when the negative electrode contains the composite solid electrolyte.

[0053] The negative electrode mixture may contain a solid electrolyte other than the composite solid electrolyte. When the negative electrode mixture contains a solid electrolyte other than the composite solid electrolyte, the lower limit of the total content of the solid electrolytes in the negative electrode mixture may be 5% by mass, and preferably 10% by mass. The upper limit of the total content of the solid electrolytes in the negative electrode mixture is preferably 90% by mass, more preferably 85% by mass, even more preferably 80% by mass, and particularly preferably 75% by mass. By setting the total content of the solid electrolytes in the above range, the electrical capacity of the all-solid-state battery can be increased.

[0054] <Other optional ingredients> The conductive agent is not particularly limited. Examples of such conductive agents include natural or artificial graphite, carbon black such as furnace black, acetylene black, and ketjen black, metals, and conductive ceramics. The conductive agent may be in the form of powder or fiber. The content of the conductive agent in the negative electrode mixture may be, for example, 0.5% by mass or more and 30% by mass or less. The negative electrode mixture may not contain a conductive agent.

[0055] The binder is not particularly limited, and examples of the binder include thermoplastic resins such as fluororesins (polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc.), polyethylene, polypropylene, polyacrylic, and polyimide; elastomers such as ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), and fluororubber; and polysaccharide polymers.

[0056] The filler is not particularly limited and examples of the filler include polyolefins such as polypropylene and polyethylene, inorganic oxides such as silicon dioxide, alumina, titanium dioxide, calcium oxide, strontium oxide, barium oxide, magnesium oxide, and aluminosilicates, hydroxides such as magnesium hydroxide, calcium hydroxide, and aluminum hydroxide, carbonates such as calcium carbonate, sparingly soluble ionic crystals such as calcium fluoride, barium fluoride, and barium sulfate, nitrides such as aluminum nitride and silicon nitride, substances derived from mineral resources such as talc, montmorillonite, boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, and mica, and artificial products thereof.

[0057] The lower limit of the average thickness of the negative electrode mixture layer 5 is preferably 30 μm, more preferably 60 μm. The upper limit of the average thickness of the negative electrode mixture layer 5 is preferably 1000 μm, more preferably 500 μm, and even more preferably 200 μm. By setting the average thickness of the negative electrode mixture layer 5 to the above lower limit or more, an all-solid-state battery having a high energy density can be obtained. By setting the average thickness of the negative electrode mixture layer 5 to the above upper limit or less, an all-solid-state battery having an anode with excellent high-rate discharge performance and high active material utilization can be obtained.

[0058] (middle class) The intermediate layer is a coating layer on the surface of the negative electrode substrate 4, and contains conductive particles such as carbon particles to reduce the contact resistance between the negative electrode substrate 4 and the negative electrode mixture layer 5. The configuration of the intermediate layer is not particularly limited, and the intermediate layer can be formed, for example, from a composition containing a resin binder and conductive particles.

[0059] [Solid electrolyte layer] The solid electrolyte layer 3 contains an electrolyte for the solid electrolyte layer. In addition to the above-mentioned composite solid electrolyte, examples of the electrolyte for the solid electrolyte layer include oxide-based solid electrolytes, other sulfide solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, and pseudo-solid electrolytes. Among these, sulfide solid electrolytes are preferred, and the composite solid electrolyte is more preferred, from the viewpoints of good ionic conductivity and ease of interface formation. By including the composite solid electrolyte in the solid electrolyte layer 3, the reduction resistance of the composite solid electrolyte can be improved while maintaining high ionic conductivity, resulting in an excellent effect of suppressing a decrease in Coulomb efficiency during charge-discharge cycles.

[0060] The electrolyte for the solid electrolyte layer may have a crystalline structure or may be amorphous without a crystalline structure. The electrolyte for the solid electrolyte layer may contain an oxide such as Li3PO4, a halogen, a halogen compound, or the like.

[0061] The lower limit of the average thickness of the solid electrolyte layer 3 is preferably 1 μm, more preferably 3 μm. The upper limit of the average thickness of the solid electrolyte layer 3 is preferably 50 μm, more preferably 20 μm. By setting the average thickness of the solid electrolyte layer 3 to the above lower limit or more, it is possible to reliably insulate the positive electrode and the negative electrode. By setting the average thickness of the solid electrolyte layer 3 to the above upper limit or less, it is possible to increase the energy density of the all-solid-state battery.

[0062] [Positive electrode] The positive electrode 2 includes a positive electrode substrate 7 and a positive electrode mixture layer 6 laminated on the surface of the positive electrode substrate 7. Similar to the negative electrode 1, the positive electrode 2 may have an intermediate layer between the positive electrode substrate 7 and the positive electrode mixture layer 6. This intermediate layer may have the same configuration as the intermediate layer of the negative electrode 1.

[0063] (Positive electrode substrate) The positive electrode substrate 7 can have the same configuration as the negative electrode substrate 4. The material of the positive electrode substrate 7 is not limited as long as it is a conductor. For example, it can be one or more metals selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, gold, silver, iron, platinum, chromium, tin, indium, alloys containing one or more of these metals, and stainless steel alloys.

[0064] The lower limit of the average thickness of the positive electrode substrate 7 is preferably 3 μm, more preferably 5 μm. The upper limit of the average thickness of the positive electrode substrate 7 is preferably 200 μm, more preferably 100 μm, and even more preferably 50 μm. By setting the average thickness of the positive electrode substrate 7 to be equal to or greater than the above lower limit, the strength of the positive electrode substrate 7 can be sufficiently increased, allowing for a satisfactory formation of the positive electrode 2. By setting the average thickness of the positive electrode substrate 7 to be equal to or less than the above upper limit, sufficient volume for the other components can be ensured.

[0065] (Positive electrode mixture layer) The positive electrode mixture layer 6 can be formed from a so-called positive electrode mixture containing a positive electrode active material. The positive electrode mixture may contain a mixture or composite containing a positive electrode active material and the sulfide solid electrolyte. The positive electrode mixture may contain the sulfide solid electrolyte that is not mixed or composite with the positive electrode active material. The sulfide solid electrolyte may be the composite solid electrolyte. Like the negative electrode mixture, the positive electrode mixture that forms the positive electrode mixture layer 6 may contain optional components such as a solid electrolyte other than the sulfide solid electrolyte, a conductive agent, a binder, a filler, etc., as necessary.

[0066] <Cathode active material> The positive electrode active material contained in the positive electrode mixture layer 6 can be a known material that is commonly used in all-solid-state batteries. The positive electrode active material is typically a material that can absorb and release lithium ions. Examples of the positive electrode active material include lithium transition metal composite oxides having an α-NaFeO2 crystal structure, lithium transition metal composite oxides having a spinel crystal structure, polyanion compounds, chalcogen compounds, and sulfur. Examples of lithium transition metal composite oxides having an α-NaFeO2 crystal structure include Li[Li x Ni 1-x ]O2(0≦x<0.5), Li[Li x Ni γ Co (1-x-γ) ]O2(0≦x<0.5, 0<γ<1), Li[Li x Co (1-x) ]O2(0≦x<0.5), Li[Li x Ni γ Mn (1-x-γ) ]O2(0≦x<0.5, 0<γ<1), Li[Li x Ni γ Mn β Co (1-x-γ-β) ]O2(0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1), Li[Li x Ni γ Co β Al (1-x-γ-β) ]O2 (0≦x<0.5, 0<γ, 0<β, 0.5<γ+β<1). Lithium transition metal composite oxides with spinel crystal structure include Li x Mn2O4, Li x Ni γ Mn (2-γ)Examples of polyanion compounds include LiFePO4, LiMnPO4, LiNiPO4, LiCoPO4, Li3V2(PO4)3, Li2MnSiO4, and Li2CoPO4F. Examples of chalcogen compounds include titanium disulfide, molybdenum disulfide, and molybdenum dioxide. Atoms or polyanions in these materials may be partially substituted with atoms or anion species of other elements. The surfaces of these materials may be coated with other materials. In the positive electrode active material layer, one of these materials may be used alone, or two or more may be mixed and used. In the positive electrode mixture layer 6, one of these compounds may be used alone, or two or more may be mixed and used.

[0067] In addition, examples of the positive electrode active material include lithium alloys such as Li-Al, Li-In, Li-Sn, Li-Pb, Li-Bi, Li-Ga, Li-Sr, Li-Si, Li-Zn, Li-Cd, Li-Ca, and Li-Ba, as well as compounds other than those represented by the above general formula, such as MnO2, FeO2, TiO2, VO5, and VO. 13 A material having a reaction potential more noble than the negative electrode material, such as TiS2, can be used.

[0068] The lower limit of the content of the positive electrode active material in the positive electrode mixture is preferably 10% by mass, more preferably 15% by mass. The upper limit of the content of the positive electrode active material is preferably 60% by mass, more preferably 70% by mass, even more preferably 80% by mass, even more preferably 90% by mass, and particularly preferably 95% by mass. By setting the content of the positive electrode active material within the above range, the electrical capacity of the all-solid-state battery can be increased.

[0069] <Mixture or Complex> The mixture is a mixture prepared by mixing the positive electrode active material and the sulfide solid electrolyte, etc., by mechanical milling, etc. For example, the mixture of the positive electrode active material and the sulfide solid electrolyte, etc., can be obtained by mixing a particulate positive electrode active material and a particulate sulfide solid electrolyte, etc. Examples of the composite include a composite having a chemical or physical bond between the positive electrode active material and the sulfide solid electrolyte, etc., and a composite obtained by mechanically combining the positive electrode active material and the sulfide solid electrolyte, etc. The composite is one in which the positive electrode active material and the sulfide solid electrolyte, etc. are present within a single particle, and examples include one in which the positive electrode active material and the sulfide solid electrolyte, etc. form an aggregated state, and one in which a coating containing the sulfide solid electrolyte, etc. is formed on at least a portion of the surface of the positive electrode active material.

[0070] When the positive electrode mixture contains a solid electrolyte, the lower limit of the solid electrolyte content may be 5 mass %, preferably 10 mass %. The upper limit of the solid electrolyte content in the positive electrode mixture is preferably 90 mass %, more preferably 85 mass %, even more preferably 80 mass %, and particularly preferably 75 mass %. By setting the solid electrolyte content within the above range, the electrical capacity of the all-solid-state battery can be increased.

[0071] The lower limit of the average thickness of the positive electrode mixture layer 6 is preferably 30 μm, more preferably 60 μm. The upper limit of the average thickness of the positive electrode mixture layer 6 is preferably 1000 μm, more preferably 500 μm, and even more preferably 200 μm. By setting the average thickness of the positive electrode mixture layer 6 to the above lower limit or more, an all-solid-state battery having a high energy density can be obtained. By setting the average thickness of the positive electrode mixture layer 6 to the above upper limit or less, an all-solid-state battery having excellent high-rate discharge performance and a positive electrode with a high active material utilization rate can be obtained.

[0072] <Method of manufacturing composite solid electrolyte> The method for producing the composite solid electrolyte includes mixing a sulfide solid electrolyte with an additive, which may be the sulfur-based cyclic compound having an S=O bond, lithium nitrate, or a combination thereof.

[0073] Examples of methods for producing the composite solid electrolyte include (1) a method in which a sulfide solid electrolyte is first synthesized, and then an additive is mixed therein to synthesize the composite solid electrolyte; and (2) a method in which a starting material for the sulfide solid electrolyte is mixed with an additive to produce a composite solid electrolyte precursor containing the additive, and then the composite solid electrolyte is synthesized from the composite solid electrolyte precursor.

[0074] (1) Method of synthesizing a composite solid electrolyte containing an additive after synthesizing a sulfide solid electrolyte In this method, the sulfide solid electrolyte synthesis step is followed by the composite solid electrolyte synthesis step.

[0075] (Sulfide solid electrolyte synthesis process) In this step, for example, the sulfide solid electrolyte is produced by the following procedure. Starting materials for the sulfide solid electrolyte (LiS, P2S5, etc.) are mixed in a predetermined molar ratio in a mortar, etc., and then the sulfide solid electrolyte is produced. Methods for producing the sulfide solid electrolyte include, for example, mechanical milling and melt quenching. In the case of producing a sulfide solid electrolyte glass ceramic, the sulfide solid electrolyte is produced and then heat-treated at a temperature equal to or higher than the crystallization temperature, whereby the sulfide solid electrolyte glass ceramic can be produced. The crystallization temperature can be determined by measurement using a differential scanning calorimeter (DSC).

[0076] (Composite solid electrolyte synthesis process) In this step, the sulfide solid electrolyte is mixed with an additive by, for example, mechanical milling, etc., to synthesize a composite solid electrolyte. The preferred range of the content of the additive in the composite solid electrolyte is as described above.

[0077] (2) A method of synthesizing a composite solid electrolyte after mixing the starting material of the sulfide solid electrolyte with an additive. In this method, starting materials for the sulfide solid electrolyte (e.g., LiS, P2S5) are mixed with additives to prepare a composite solid electrolyte precursor containing the additives. The composite solid electrolyte can then be produced by, for example, mechanical milling, melt quenching, or heat treatment.

[0078] The method for producing a composite solid electrolyte includes mixing a sulfide solid electrolyte with the additive to produce a composite solid electrolyte, and therefore it is possible to produce a composite solid electrolyte that is reduction-resistant and has an excellent effect of suppressing a decrease in coulomb efficiency during the charge-discharge cycle of an all-solid-state battery.

[0079] <Manufacturing method for all-solid-state batteries> The method for producing an all-solid-state battery includes fabricating at least one of an anode and an electrolyte layer using the composite solid electrolyte or a composite solid electrolyte obtained by the method for producing the composite solid electrolyte. The method for producing an all-solid-state battery may also include other steps, such as a step of preparing an anode mixture, a step of preparing an electrolyte for a solid electrolyte layer, a step of preparing a cathode mixture, and a step of stacking an anode, a solid electrolyte layer, and a cathode. Details of the composite solid electrolyte and the composite solid electrolyte obtained by the method for producing the composite solid electrolyte are as described above.

[0080] (Negative electrode mixture production process) In this step, an anode mixture for forming an anode is prepared. When the anode mixture contains a mixture or composite including an anode active material and the composite solid electrolyte, this step includes, for example, mixing the anode active material and the composite solid electrolyte using a mechanical milling method or the like to prepare a mixture or composite of the anode active material and the composite solid electrolyte. Alternatively, the anode mixture may be prepared without using the mechanical milling method. In this case, for example, the method may include preparing an anode mixture paste containing an anode active material, a solid electrolyte, a conductive agent, etc., and applying the paste to an anode substrate. When the anode mixture contains the composite solid electrolyte, the composite solid electrolyte or a composite solid electrolyte obtained by the method for producing the composite solid electrolyte is used.

[0081] (Solid electrolyte layer manufacturing process) In this process, a solid electrolyte layer is produced. In this process, the solid electrolyte layer can be obtained by processing a predetermined material for the solid electrolyte layer electrolyte using a mechanical milling method. The solid electrolyte layer electrolyte may also be produced by heating the predetermined material for the solid electrolyte layer electrolyte above its melting temperature using a melt-quenching method, melting and mixing the two in a predetermined ratio, and then quenching. Other methods for synthesizing the solid electrolyte layer electrolyte include, for example, a solid-phase method in which the solid electrolyte layer is sealed under reduced pressure and then fired, a liquid-phase method such as solution deposition, a vapor-phase method (PLD), and a method in which the solid electrolyte layer is fired in an argon atmosphere after mechanical milling. When the solid electrolyte layer electrolyte is a composite solid electrolyte, the composite solid electrolyte or a composite solid electrolyte obtained by the method for producing the composite solid electrolyte is used as the solid electrolyte layer electrolyte.

[0082] (Positive electrode mixture production process) In this process, a cathode mixture for forming a cathode is prepared. The method for preparing the cathode mixture is not particularly limited and can be appropriately selected depending on the purpose. Examples include compression molding of a cathode active material, mechanical milling of a predetermined material for the cathode mixture, and sputtering using a target material for the cathode active material. When the cathode mixture contains a mixture or composite containing a cathode active material and a sulfide solid electrolyte, this process includes, for example, mixing the cathode active material and the sulfide solid electrolyte using a mechanical milling method or the like to prepare a mixture or composite of the cathode active material and the sulfide solid electrolyte. Similarly to the negative electrode mixture preparation process, the cathode mixture may also be prepared without using the mechanical milling method. In this case, for example, the process may include preparing a cathode mixture paste containing a cathode active material, a solid electrolyte, a conductive agent, etc., and applying the paste to a cathode substrate.

[0083] (Lamination process) In this step, a negative electrode having a negative electrode substrate and a negative electrode mixture layer, a solid electrolyte layer, and a positive electrode having a positive electrode substrate and a positive electrode mixture layer are laminated. In this step, the negative electrode, the solid electrolyte layer, and the positive electrode may be laminated in this order or vice versa, and the order of lamination of the layers is not particularly important. The negative electrode is formed, for example, by pressure molding the negative electrode substrate and the negative electrode mixture, the solid electrolyte layer is formed, for example, by pressure molding an electrolyte for the solid electrolyte layer, and the positive electrode is formed, for example, by pressure molding the positive electrode substrate and the positive electrode mixture.

[0084] The negative electrode, the solid electrolyte layer, and the positive electrode may be laminated by simultaneously pressure-molding the negative electrode substrate, the negative electrode mixture, the electrolyte for the solid electrolyte layer, the positive electrode substrate, and the positive electrode mixture. Alternatively, the positive electrode, the negative electrode, or a layer thereof may be molded in advance, and then pressure-molded together with the solid electrolyte layer to laminate them.

[0085] The method for producing an all-solid-state battery includes producing at least one of a negative electrode and an electrolyte layer using the composite solid electrolyte or the composite solid electrolyte obtained by the method for producing the composite solid electrolyte, and therefore it is possible to produce an all-solid-state battery that has an excellent effect of suppressing a decrease in coulombic efficiency during charge-discharge cycles.

[0086] [Other embodiments] The present invention is not limited to the above-described embodiment, and can be practiced in various forms with various modifications and improvements in addition to the above-described embodiment.

[0087] The all-solid-state battery according to the present invention may also include layers other than the negative electrode, positive electrode, and solid electrolyte layer, such as an intermediate layer or an adhesive layer, as other components.

[0088] <Example> The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0089] [Preparation of composite solid electrolyte] Example 1 Li2S (99.98 mass%, Aldrich) and P2S5 (99 mass%, Aldrich) were weighed in a 75:25 molar ratio in a glove box with an argon atmosphere at a dew point below -50°C and mixed in a mortar. This mixed sample was placed in a sealed zirconia pot. Milling was carried out for 45 hours at a revolution speed of 510 rpm in a planetary ball mill (FRITSCH, Model No. Premium Line P-7) to obtain 75Li2S 25P2S5.

[0090] Next, 75Li2S·25P2S5 and lithium nitrate as an additive were weighed and mixed in a mass ratio of 90:10, and then mechanically milled using a planetary ball mill at an orbital rotation speed of 370 rpm for 2 hours to synthesize the composite solid electrolyte of Example 1.

[0091] Example 2 A composite solid electrolyte of Example 2 was synthesized in the same manner as in Example 1, except that the additive was changed to 1,3-propene sultone (PRS), which is a cyclic sulfonic acid ester.

[0092] (Comparative Example 1) The 75Li2S·25P2S5 in Example 1 before mixing with the additive was used as Comparative Example 1.

[0093] (Comparative Example 2) A composite solid electrolyte of Comparative Example 2 was synthesized in the same manner as in Example 1, except that the additive was changed to lithium iodide.

[0094] [Fabrication of a cell for evaluating reduction resistance] 120 mg of each of the solid electrolytes of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 was inserted into a polycarbonate tube with an inner diameter of 10 mm, and then pressure-molded at 360 MPa. After releasing the pressure, a metal Li foil was attached to the counter electrode side, and a metal In foil was attached to the working electrode side, and then pressure-molded at 120 MPa to obtain pellets. These were inserted into a Hohsen HS cell to prepare a cell for evaluating reduction resistance. The pellets in each reduction resistance evaluation cell were pressurized at about 5 MPa by a spring in the HS cell.

[0095] [evaluation] (Charge / discharge cycle test: Coulomb efficiency) (1) Charge / discharge cycle test Each reduction resistance evaluation cell was stored in a constant temperature bath at 50°C for 30 minutes, and then subjected to a current density of 0.1 mAhcm -1 A constant current / constant voltage charge / discharge was performed for 10 hours. The charge cut-off voltage for charging was 0.2 V. The discharge cut-off voltage for discharging was 1.1 V. A 30-minute pause was provided after each charge and discharge step. These charge and discharge steps constitute one cycle, and three cycles were repeated for Example 1, Example 2, and Comparative Example 1, and four cycles were repeated for Comparative Example 2. The charge, discharge, and pause were all performed in a constant temperature bath at 50°C. (2) Coulomb efficiency For each of the reduction resistance evaluation cells in the charge-discharge cycle test, the percentage of the discharge capacity (Ah) in the first to fifth cycles relative to the amount of charge electricity (Ah) in the first to fifth cycles was calculated as the "Coulomb efficiency (%)" in the first to fifth cycles. The results are shown in Figure 2.

[0096] As shown in FIG. 2 , the composite solid electrolytes of Examples 1 and 2, which contained a sulfur-based cyclic compound having an S═O bond or lithium nitrate as an additive, were superior in the effect of suppressing the decrease in coulombic efficiency during charge-discharge cycles compared to Comparative Example 1, which contained no additive, and Comparative Example 2, which contained lithium iodide as an additive.

[0097] The above results demonstrate that the composite solid electrolyte according to one aspect of the present invention can suppress the decrease in coulombic efficiency during the charge-discharge cycle of an all-solid-state battery. [Industrial Applicability]

[0098] The composite solid electrolyte and all-solid-state battery according to the present invention have an excellent effect of suppressing the decrease in coulomb efficiency during charge-discharge cycles, and are therefore suitable for use, for example, as all-solid-state batteries for HEVs and solid electrolytes used therein. [Explanation of symbols]

[0099] 1 negative electrode 2 Positive electrode 3 Solid electrolyte layer 4. Negative electrode substrate 5. Negative electrode mixture layer 6 Positive electrode mixture layer 7. Positive electrode substrate 10 All-solid-state battery

Claims

1. A sulfide solid electrolyte and an additive are included, the additive is a sulfur-based cyclic compound having an S═O bond, The composite solid electrolyte wherein the sulfur-based cyclic compound is 1,3-propene sultone (However, this does not include the case where the sulfide solid electrolyte comprises (Li 2 S) l -(P 2 S 5 ) m -(YX 2 ) n (Y is at least one selected from the group consisting of Ge, Si and Sn, X is at least one selected from the group consisting of S, Se and Te, l, m and n are each 0 or greater, and at least two of l, m and n are greater than 0), and is contained in an electrolyte solution containing a solvent and a lithium salt as a solvent-soluble precursor).

2. A sulfide solid electrolyte and an additive are included, the additive is a sulfur-based cyclic compound having an S═O bond, A composite solid electrolyte in which the content of the additive exceeds 5 mass %. (However, this does not include the case where the sulfide solid electrolyte comprises (Li 2 S) l -(P 2 S 5 ) m -(YX 2 ) n (Y is at least one selected from the group consisting of Ge, Si and Sn, X is at least one selected from the group consisting of S, Se and Te, l, m and n are each 0 or greater, and at least two of l, m and n are greater than 0), and is contained in an electrolyte solution containing a solvent and a lithium salt as a solvent-soluble precursor).

3. A sulfide solid electrolyte and an additive are included, the additive is lithium nitrate, A composite solid electrolyte having a content of the additive exceeding 5% by mass.

4. A sulfide solid electrolyte and an additive are included, the additive is lithium nitrate, Composite solid electrolyte for the negative electrode (However, this does not include the case where the sulfide solid electrolyte comprises (Li 2 S) l -(P 2 S 5 ) m -(YX 2 ) n (Y is at least one selected from the group consisting of Ge, Si and Sn, X is at least one selected from the group consisting of S, Se and Te, l, m and n are each 0 or greater, and at least two of l, m and n are greater than 0), and is contained in an electrolyte solution containing a solvent and a lithium salt as a solvent-soluble precursor).

5. 5. The composite solid electrolyte according to claim 1, wherein the content of the additive in the composite solid electrolyte is 20 mass % or less.

6. 3. The composite solid electrolyte according to claim 2, wherein the sulfur-based cyclic compound is a cyclic sulfonate ester.

7. a negative electrode, a positive electrode, and an electrolyte layer interposed between the negative electrode and the positive electrode; 7. An all-solid-state battery, wherein the negative electrode, the electrolyte layer, or a combination thereof contains the composite solid electrolyte according to claim 1.

8. mixing a sulfide solid electrolyte with an additive to prepare a composite solid electrolyte; the additive is a sulfur-based cyclic compound having an S═O bond, Method for producing a composite solid electrolyte in which the sulfur-based cyclic compound is 1,3-propene sultone (However, this does not include the case where the sulfide solid electrolyte comprises (Li 2 S) l -(P 2 S 5 ) m -(YX 2 ) n (Y is at least one selected from the group consisting of Ge, Si and Sn, X is at least one selected from the group consisting of S, Se and Te, l, m and n are each 0 or greater, and at least two of l, m and n are greater than 0), and is contained in an electrolyte solution containing a solvent and a lithium salt as a solvent-soluble precursor).

9. mixing a sulfide solid electrolyte with an additive to prepare a composite solid electrolyte; the additive is a sulfur-based cyclic compound having an S═O bond, A method for producing a composite solid electrolyte in which the content of the additive exceeds 5 mass % (However, this does not include the case where the sulfide solid electrolyte comprises (Li 2 S) l -(P 2 S 5 ) m -(YX 2 ) n (Y is at least one selected from the group consisting of Ge, Si and Sn, X is at least one selected from the group consisting of S, Se and Te, l, m and n are each 0 or greater, and at least two of l, m and n are greater than 0), and is contained in an electrolyte solution containing a solvent and a lithium salt as a solvent-soluble precursor).

10. mixing a sulfide solid electrolyte with an additive to prepare a composite solid electrolyte; the additive is lithium nitrate, A method for producing a composite solid electrolyte, wherein the content of the additive exceeds 5 mass %.

11. mixing a sulfide solid electrolyte with an additive to prepare a composite solid electrolyte; the additive is lithium nitrate, A method for manufacturing a composite solid electrolyte for use as an anode (However, this does not include the case where the sulfide solid electrolyte comprises (Li 2 S) l -(P 2 S 5 ) m -(YX 2 ) n (Y is at least one selected from the group consisting of Ge, Si and Sn, X is at least one selected from the group consisting of S, Se and Te, l, m and n are each 0 or greater, and at least two of l, m and n are greater than 0), and is contained in an electrolyte solution containing a solvent and a lithium salt as a solvent-soluble precursor).

12. The method for producing a composite solid electrolyte according to any one of claims 8 to 11, wherein a content of the additive in the composite solid electrolyte is 20 mass % or less.

13. 13. A method for producing an all-solid-state battery, comprising: producing at least one of a negative electrode and an electrolyte layer using the composite solid electrolyte according to any one of claims 1 to 6 or the composite solid electrolyte obtained by the method for producing a composite solid electrolyte according to any one of claims 8 to 12.

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