Conductive composite material for sulfide solid-state batteries and method for manufacturing conductive composite material for sulfide solid-state batteries

Abstract

In sulfide solid-state batteries, coating the conductive material contained in the positive electrode active material layer for sulfide solid-state batteries with a coating material can suppress the deterioration of the interface between the conductive material and the sulfide solid electrolyte. Therefore, the present disclosure aims to provide a novel conductive composite material for sulfide solid-state batteries having a coating material that can improve the performance of sulfide solid-state batteries when used in such batteries. [Solution] A conductive composite material 110 for a sulfide solid battery, comprising a conductive material 111 and a coating material 112 covering the surface of the conductive material 111, wherein the coating material 112 is a lithium compound.

Description

[Technical Field]

[0001] This disclosure relates to a conductive composite material for sulfide solid-state batteries and a method for manufacturing a conductive composite material for sulfide solid-state batteries. [Background technology]

[0002] Secondary batteries using sulfide solid electrolytes exhibit high moldability and ionic conductivity. However, in such secondary batteries, if the interface between the active material and the sulfide solid electrolyte in the electrode deteriorates, the interfacial resistance increases, leading to a decrease in ionic conductivity within the electrode. To address this, a commonly known method involves coating the active material with an oxide such as LiNbO3 to protect the interface.

[0003] Furthermore, the interface between the conductive material and the sulfide solid electrolyte also needs to be protected to prevent a decrease in electronic conductivity due to degradation. Patent Document 1 discloses a sulfide solid battery comprising a positive electrode layer containing a positive electrode composite material, a negative electrode layer, and a sulfide solid electrolyte layer existing between the positive electrode layer and the negative electrode layer, wherein the positive electrode composite material contains a high-potential positive electrode active material whose surface is coated with an oxide, a carbon conductive material, and a sulfide solid electrolyte, and the carbon conductive material is characterized in that its surface is provided with a coating layer containing Nb2O5 or Al2O3. According to Patent Document 1, by providing a coating layer containing Nb2O5 or Al2O3 on the carbon conductive material, the coating layer does not enter a high-potential state, so the decomposition of the sulfide solid electrolyte and the release of sulfur components caused by contact between the carbon conductive material and the sulfide solid electrolyte are suppressed, and as a result the generation of high-resistance substances due to the reaction between the released sulfur components and the high-potential positive electrode active material is suppressed, so the capacity retention rate can be improved compared to conventional batteries.

[0004] On the other hand, lithium secondary batteries in which a conductive material is coated with lithium carbonate are known. Patent Document 2 discloses a lithium secondary battery equipped with a current interruption mechanism that operates due to an increase in internal pressure, wherein the positive electrode constituting the battery has a positive electrode composite layer containing a positive electrode active material mainly composed of lithium transition metal oxide, a conductive material, and lithium carbonate, and the lithium carbonate is arranged on the surface of the conductive material. The lithium secondary battery of Patent Document 2 is said to have better battery performance because it is equipped with a current interruption mechanism that operates due to an increase in internal pressure. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-055926 [Patent Document 2] Japanese Patent Publication No. 2010-171020 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] When a high-potential positive electrode active material is used to increase the capacity of a sulfide solid battery, the conductive material also becomes high-potential. This can lead to the sulfide solid electrolyte decomposing more easily at the interface between the conductive material and the sulfide solid electrolyte, potentially reducing battery performance. To suppress this problem, Patent Document 1 proposes forming a coating layer containing Nb2O5 or Al2O3 on the surface of the conductive material.

[0007] However, for such coating layers, it may be preferable to use materials other than Nb2O5 or Al2O3.

[0008] In contrast, this disclosure provides a conductive composite material for sulfide solid-state batteries having a novel coating material.

[0009] In addition, Patent Document 1 lists the atomic layer deposition method (ALD) as an example of a method for coating a conductive material with a coating material. However, although ALD has the characteristic of being able to form a uniform film by precisely controlling the film thickness, it has the problems of a slow film formation rate and low productivity.

[0010] In contrast, the present disclosure provides a method for efficiently manufacturing a conductive composite material for a sulfide solid battery having a novel coating material.

[0011] Note that Patent Document 2 proposes using a conductive material having lithium carbonate disposed on its surface in order to manufacture a lithium secondary battery provided with a current interruption mechanism that operates due to an increase in internal pressure, but does not consider the decomposition of the sulfide solid electrolyte when using a high-potential positive electrode active material.

Means for Solving the Problems

[0012] The present disclosure achieves the above object by the following means. 〈Aspect 1〉 A conductive composite material for a sulfide solid battery, having a conductive material and a coating material covering the surface of the conductive material, and wherein the coating material is a lithium compound. A conductive composite material for a sulfide solid battery. 〈Aspect 2〉 The conductive composite material for a battery according to Aspect 1, wherein the coating material is selected from lithium carbonate, lithium hexafluorophosphate, lithium chloride, lithium tetrafluoroborate, lithium phosphate, and lithium niobate, and combinations thereof. 〈Aspect 3〉 A positive electrode active material layer for a sulfide solid battery, comprising the conductive composite material for a sulfide solid battery according to Aspect 1 or 2, a positive electrode active material, and a sulfide solid electrolyte. 〈Aspect 4〉 Coating a coating material on the surface of the conductive material, and heating the coating material until the temperature of the coating material reaches [(melting point of the coating material or decomposition temperature of the coating material) - 120] °C or higher, and wherein the coating material is a lithium compound. A method for manufacturing conductive composite materials for sulfide solid-state batteries. <Aspect 5> The method according to embodiment 4, wherein the coating material is selected from lithium carbonate, lithium hexafluoride phosphate, lithium chloride, lithium tetrafluoroborate, lithium phosphate, and lithium niobate, and combinations thereof. [Effects of the Invention]

[0013] According to this disclosure, it is possible to provide a conductive composite material for sulfide solid-state batteries having a novel coating material. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a schematic diagram illustrating the conductive composite material for batteries of the present disclosure. [Modes for carrying out the invention]

[0015] The embodiments of this disclosure will be described in detail below. However, this disclosure is not limited to the embodiments described below and can be implemented in various ways within the scope of the gist of this disclosure.

[0016] 《Conductive composite material for sulfide solid state batteries》 It has a conductive material and a coating material covering the surface of the conductive material, and The above coating material is a lithium compound. Conductive composite material for sulfide solid state batteries.

[0017] According to this disclosure, it is possible to provide a conductive composite material for sulfide solid-state batteries having a novel coating material.

[0018] In a sulfide solid-state battery, when the positive electrode active material is at a high potential, the conductive material in contact with the positive electrode active material will also be at a high potential. Therefore, when the highly potential conductive material comes into contact with the sulfide solid electrolyte, that potential is applied to the sulfide solid electrolyte, causing it to decompose and degrading the battery performance.

[0019] Therefore, the disclosers have found that coating a conductive material with a lithium compound suppresses the decomposition of the sulfide solid electrolyte. Furthermore, when the conductive composite material for sulfide solid batteries of this disclosure is applied to a lithium-ion battery, the lithium compound is less likely to act as an impurity in the positive electrode active material layer for the sulfide solid battery, thus improving the overall performance of the sulfide solid battery.

[0020] Specifically, as shown in Figure 1, the sulfide solid battery 100 comprises a conductive composite material 110 for sulfide solid batteries, a sulfide solid electrolyte 120, and a positive electrode active material 130. The conductive composite material 110 for sulfide solid batteries is formed by coating a conductive material 111 with a coating material 112. Decomposition of the sulfide solid electrolyte 120 due to the application of potential from the conductive material 111 is suppressed by the coating material 112. In addition, the positive electrode active material 130 is coated with a coating material 140 for positive electrode active material. Decomposition of the sulfide solid electrolyte 120 due to the application of potential from the positive electrode active material 130 is also suppressed by the coating material 140 for positive electrode active material.

[0021] Furthermore, lithium compounds can be dissolved in solvents such as water or organic solvents, and by coating the conductive material with this solution and drying it, the lithium compound can be applied to the conductive material. Therefore, conductive composite materials for sulfide solid-state batteries in which the coating material is a lithium compound have lower manufacturing costs compared to conductive composite materials for sulfide solid-state batteries in which the coating method is limited to atomic layer deposition (ALD).

[0022] In this disclosure, "sulfide solid battery" means a battery that uses at least a sulfide solid electrolyte as the electrolyte, and therefore a sulfide solid battery may use a combination of a sulfide solid electrolyte and a liquid electrolyte as the electrolyte. Furthermore, a sulfide solid battery may be a lithium-ion battery.

[0023] The conductive composite material for sulfide solid-state batteries of this disclosure comprises a conductive material and a coating material that covers the surface of the conductive material.

[0024] The amount of coating material covering the conductive material is not particularly limited and may be 0.5% by mass or more, 1.0% by mass or more, 3.0% by mass or more, 5.0% by mass or more, or 10% by mass or more relative to the mass of the conductive material, and may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 15% by mass or less.

[0025] <Coating material> The coating material is a lithium compound. In this disclosure, "coating material" means a material that is coated on a conductive material, in particular a material that is coated on a conductive material for the purpose of suppressing the decomposition of the sulfide solid electrolyte. The coating material is preferably a material that can exist stably at the charge-discharge potential of the sulfide solid electrolyte and does not interfere with electron transfer between the positive electrode active material and the conductive material.

[0026] The lithium compound is a lithium-containing compound and may be selected from, for example, lithium carbonate (Li2CO3), lithium hexafluoride phosphate (LiPF6), lithium chloride (LiCl), lithium tetrafluoroborate (LiBF4), lithium phosphate (LiPO3, Li3PO4), and lithium niobate (LiNbO3), as well as combinations thereof.

[0027] <Conductive materials> The conductive material may be selected from carbon powder, carbon fiber, metal powder, or combinations thereof.

[0028] The carbon powder may be, for example, acetylene black (AB), furnace black (FB), Ketjen black (KB), etc.

[0029] Carbon fibers may be, for example, vapor-grown carbon fibers (VGCF), carbon nanofibers (CNF), carbon nanotubes (CNT), etc.

[0030] The metal powder may be a conductive metal powder, such as nickel powder.

[0031] The particle size of the conductive material is not particularly limited. Average particle size D of the conductive material

[0036] , 2 , , 2 ,

[0035] , , , , , , , 2 , 2 , , , 2 ,

[0034] ,

[0037] may be, for example, 10 nm or more, 20 nm or more, 20 nm or more, 30 nm or more, or 50 nm or more, and may be 200 nm or less, 150 nm or less, or 100 nm or less.

[0032] Here, the average particle diameter D 50 is the particle diameter (median diameter) at the integrated value of 50% in the volume-based particle size distribution determined by the laser diffraction / scattering method. [[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​The positive electrode active material layer for sulfide solid-state batteries comprises at least the conductive composite material for sulfide solid-state batteries, the positive electrode active material, and the sulfide solid electrolyte as disclosed herein, and may optionally contain a binder, various other additives, etc. The respective content of the conductive composite material for sulfide solid-state batteries, the positive electrode active material, the sulfide solid electrolyte, the binder, various additives, etc., can be appropriately determined according to the desired battery performance. For the conductive composite material for sulfide solid-state batteries disclosed herein, refer to the above description relating to the conductive composite material for sulfide solid-state batteries.

[0038] The content of the conductive composite material for sulfide solid batteries of this disclosure in the positive electrode active material layer for sulfide solid batteries is not particularly limited. For example, it may be 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 2.0% by mass or more, 3.0% by mass or more, or 10.0% by mass or less, 8.0% by mass or less, 6.0% by mass or less, or 5.0% by mass or less, based on the mass of the positive electrode active material layer for sulfide solid batteries.

[0039] The content of the positive electrode active material in the positive electrode active material layer for sulfide solid-state batteries is not particularly limited. For example, it may be 40% by mass or more, 50% by mass or more, or 60% by mass or more, and may be 98% by mass or less, 95% by mass or less, or 90% by mass or less, based on the mass of the positive electrode active material layer for sulfide solid-state batteries.

[0040] The shape of the positive electrode active material layer for sulfide solid-state batteries is not particularly limited, but may be, for example, a sheet-shaped positive electrode active material layer for sulfide solid-state batteries. The thickness of the positive electrode active material layer for sulfide solid-state batteries is not particularly limited, but may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or more, or 2 mm or less, 1 mm or less, or 500 μm or less.

[0041] The positive electrode active material layer for sulfide solid-state batteries can be manufactured by applying known methods. For example, the positive electrode active material layer for sulfide solid-state batteries may be manufactured by molding a composition (positive electrode mixture) containing a conductive composite material for sulfide solid-state batteries, a positive electrode active material, a sulfide solid electrolyte, and various additives. Alternatively, the positive electrode active material layer for sulfide solid-state batteries may be manufactured by generating a positive electrode mixture slurry by mixing the positive electrode mixture with a dispersion medium, and then applying and drying the positive electrode mixture slurry.

[0042] In this disclosure, “positive electrode mixture” means a composition that can constitute a positive electrode active material layer for a sulfide solid battery, either as is or by further containing other components. In this disclosure, “positive electrode mixture slurry” means a slurry that contains a dispersion medium in addition to the “positive electrode mixture,” and can be applied and dried to form a positive electrode active material layer for a sulfide solid battery.

[0043] (Cathode active material) The material of the positive electrode active material is not particularly limited as long as it is capable of intercalating and releasing lithium ions. Examples of positive electrode active materials include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), and nickel-cobalt-manganese oxide (NCM:LiCO2). 1 / 3 Ni 1 / 3 Mn 1 / 3 O2), lithium nickel-cobalt aluminum oxide (LiNi 0.8 (CoAl) 0.2 O2), Li 1+x Mn 2-x-y M y This may include, but is not limited to, heteroatom-substituted Li-Mn spinel with a composition represented by O4 (where M is one or more metallic elements selected from Al, Mg, Co, Fe, Ni, and Zn).

[0044] The positive electrode active material is not particularly limited, but may have a coating layer. The coating layer is a layer containing a material that has lithium ion conductivity, low reactivity with the positive electrode active material and sulfide solid electrolyte, and can maintain a coating layer form that does not flow even when in contact with the positive electrode active material and sulfide solid electrolyte. Specific examples of materials constituting the coating layer include LiNbO3 and Li4Ti5O3. 12 Examples include Li3PO4, but are not limited to these.

[0045] The shape of the positive electrode active material is not particularly limited, as long as it is a shape common for positive electrode active materials in batteries. The positive electrode active material may be, for example, particulate. The positive electrode active material may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle diameter D of the positive electrode active material 50 For example, it may be 1 nm or more, 5 nm or more, or 10 nm or more, and it may also be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less.

[0046] Here, the average particle diameter D 50 This is the particle diameter (median diameter) at 50% of the integrated value in the volume-based particle size distribution determined by laser diffraction and scattering.

[0047] (Sulfide solid electrolyte) The material of the sulfide solid electrolyte is not particularly limited and may be, for example, a sulfide-based amorphous solid electrolyte, a sulfide-based crystalline solid electrolyte, or an argyrodite-type solid electrolyte. A specific example of a sulfide solid electrolyte is the Li2S-P2S5 system (Li7P3S 11 , Li3PS4, Li8P2S9, etc.), Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-LiBr-Li2S-P2S5, Li2S-P2S5-GeS2(Li 13 GeP3S 16 Li 10 GeP2S 12 ), LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li 7-x PS 6-x Cl xEtc.; or combinations thereof, but not limited to these.

[0048] The sulfide solid electrolyte may be glass or crystallized glass (glass ceramics).

[0049] (Binder) The binder is not particularly limited, but may be made of materials such as polyvinylidene fluoride (PVDF), butadiene rubber (BR), polytetrafluoroethylene (PTFE), or styrene-butadiene rubber (SBR). The binder is not particularly limited, but may be used alone or in combination of two or more types.

[0050] Method for manufacturing conductive composite materials for sulfide solid-state batteries A coating material is applied to the surface of the conductive material, and Heat the above-mentioned coating material until its temperature reaches [(melting point or decomposition temperature of the coating material) - 120]°C or higher. including and The above coating material is a lithium compound. A method for manufacturing conductive composite materials for sulfide solid-state batteries.

[0051] The method disclosed herein enables the production of the conductive composite material for sulfide solid-state batteries of this disclosure with high productivity.

[0052] The Disclosers have found that by using a conductive composite material for batteries, obtained by coating a conductive material with a coating material and then heating the coating material to a predetermined temperature, in a solid-state battery, a significant effect in preventing the degradation of the sulfide solid electrolyte can be obtained. Although not limited to theory, it is thought that even if the coating material does not uniformly cover the conductive material before heating, and there are parts of the conductive material that are exposed, the coating material softens and deforms into a thin, spreadable material when heated to a high temperature, and the exposed parts of the conductive material are covered by the coating material, resulting in a uniformly covered state and thus an enhanced protective effect on the sulfide solid electrolyte.

[0053] Furthermore, by including a step to heat the coating material, the preceding step of coating the coating material with a conductive material eliminates the need to use high-precision coating methods such as atomic layer deposition (ALD). Instead, a simpler method with a shorter film formation time can be selected, such as coating a solution of the coating material dissolved in a solvent, thereby increasing productivity.

[0054] <Coating Process> The present disclosure of a method for producing a conductive composite material for sulfide solid-state batteries includes coating a coating material onto the surface of a conductive material. The coating material is a lithium compound. The lithium compound may be selected from, for example, lithium carbonate (Li2CO3), lithium hexafluoride phosphate (LiPF6), lithium chloride (LiCl), lithium tetrafluoroborate (LiBF4), lithium phosphate (LiPO3, Li3PO4), and lithium niobate (LiNbO3), as well as combinations thereof. The composition of the conductive material and the coating material can be found in the above description relating to conductive composite materials for sulfide solid-state batteries.

[0055] The coating method is not particularly limited, and the coating may be applied by mixing the coating material with a conductive material and dissolving the coating material in a solvent. For example, when lithium carbonate is used as the coating material, the coating can be applied by mixing the conductive material and lithium carbonate, dissolving the lithium carbonate in pure water, and drying it at 100°C for 2 hours.

[0056] <Heating process> The present disclosure's method for manufacturing a conductive composite material for batteries includes heating the coating material until its temperature reaches [(melting point or decomposition temperature of the coating material)-120]°C or higher. Here, "melting point or decomposition temperature of the coating material" means the lower of the melting point of the coating material and the decomposition temperature of the coating material. The temperature of the coating material may be [(melting point or decomposition temperature of the coating material)-110]°C or higher, [(melting point or decomposition temperature of the coating material)-100]°C or higher, [(melting point or decomposition temperature of the coating material)-80]°C or higher, [(melting point or decomposition temperature of the coating material)-50]°C or higher, or [(melting point or decomposition temperature of the coating material)-20]°C or higher, or [(melting point or decomposition temperature of the coating material)+100]°C or lower, [(melting point or decomposition temperature of the coating material)+80]°C or lower, or [(melting point or decomposition temperature of the coating material)+50]°C or lower. The coating material may also be melted.

[0057] The heating method described above is not particularly limited. For example, when lithium carbonate is used as the coating material, it may be heated in an electric furnace in an argon atmosphere at a rate of 200°C / h up to 620°C. Also, if the coating process includes a drying process, the drying process and the heating process may be performed simultaneously.

[0058] The time for maintaining the temperature of the above-mentioned covering material is not particularly limited and may be, for example, 2 hours or more, 3 hours or more, 4 hours or more, 5 hours or more, 20 hours or less, 15 hours or less, or 10 hours or less.

[0059] The method for cooling the conductive material coated with the molten coating is not particularly limited and may be, for example, natural cooling. [Examples]

[0060] The present disclosure will be specifically illustrated by examples and comparative examples, but will not be limited thereto.

[0061] Manufacturing of conductive composite materials for sulfide solid-state batteries <Example 1> Using lithium hexafluoride phosphate as a coating material and VGCF as a conductive material, a mixture was prepared with a weight ratio of lithium hexafluoride phosphate:VGCF = 1:9. After dissolving the lithium hexafluoride phosphate in dimethyl carbonate at a concentration of 3 mol / L, it was dried at 100°C for 2 hours to produce a conductive composite material for sulfide solid-state batteries as Example 1.

[0062] <Example 2> A conductive composite material for a sulfide solid-state battery, designated as Example 2, was manufactured in the same manner as in Example 1, except that lithium carbonate was used as a coating material instead of the conductive composite material for a sulfide solid-state battery in Example 1, and the lithium carbonate was dissolved in pure water.

[0063] <Example 3> Lithium carbonate as a coating material and VGCF as a conductive material were mixed in a weight ratio of lithium carbonate:VGCF = 1:9. The lithium carbonate was dissolved in pure water and then dried at 100°C for 2 hours to obtain VGCF coated with lithium carbonate. Subsequently, the VGCF coated with lithium carbonate was heated in an electric furnace in an Ar atmosphere at 200°C / h to 620°C, held at 620°C for 2 hours, and then allowed to cool naturally to produce the conductive composite material for sulfide solid-state batteries as Example 3.

[0064] <Example 4> A conductive composite material for a battery, designated as Example 4, was manufactured in the same manner as in Example 3, except that lithium chloride was used as the coating material instead of the conductive composite material for a sulfide solid-state battery in Example 3, and the coating material was dissolved in ethanol. <Comparative Example 1> As Comparative Example 1, we prepared VGCF, a conductive material without a coating.

[0065] "evaluation" <Evaluation of conductive composite materials for sulfide solid-state batteries> The conductive composite materials or conductive materials for sulfide solid batteries from Examples 1-4 and Comparative Example 1 were mixed with sulfide solid electrolytes in a weight ratio of 1:9, respectively, in a mortar and pestle to prepare the evaluation mixture. Next, 20 mg of the evaluation mixture was placed in an evaluation apparatus equipped with a stainless steel current collector and a non-conductive ceramic guide to form the evaluation layer. A half-cell was then constructed using the evaluation layer, a sulfide-based solid electrolyte as the electrolyte layer, and an indium-lithium alloy as the counter electrode.

[0066] At an ambient temperature of 25°C and a sweep speed of 1mV / s, the upper limit voltage is 5V (vs.Li / Li + By applying a voltage up to ) and performing cyclic voltammetry measurements, the amount of electricity (mAh / g) required for the decomposition reaction of the sulfide solid electrolyte per unit amount of composite material used for evaluation was determined, and the degree of degradation of the unit sulfide solid electrolyte was evaluated.

[0067] <Evaluation of positive electrode active material layer for sulfide solid-state batteries> The conductive composite materials or conductive materials for batteries in Examples 1-4 and Comparative Example 1 are used as positive electrode active materials for sulfide solid batteries, and LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523) and an argyrodite-based solid electrolyte were mixed in a weight ratio of 1:70:29, respectively, and then mixed in a mortar to create an evaluation mixture. Next, 17 mg of the evaluation mixture was placed in an evaluation apparatus equipped with a stainless steel current collector and a non-conductive ceramic guide to form the positive electrode active material layer for the sulfide solid battery. Then, a half-cell was constructed using the positive electrode active material layer for the sulfide solid battery, an argyrodite-based solid electrolyte as the sulfide solid electrolyte layer, and an indium-lithium alloy as the counter electrode.

[0068] Ambient temperature 25°C, C-rate 0.1C (0.2mA / cm²) 2 ), charging termination voltage 4.35V (vsLi + The above half-cell was charged with a constant current under the condition of / Li, and the initial charge capacity was measured.

[0069] Under ambient temperature of 25°C and discharge termination voltage of 3.00V, a half-cell that had completed initial charging was discharged, and the initial discharge capacity was measured. The initial charge-discharge efficiency (%) was calculated by [initial discharge capacity] / [initial charge capacity] × 100.

[0070] Float charging was performed for 120 hours under ambient temperature of 60°C and charging voltage of 4.35V. Then, under ambient temperature of 25°C, C-rate of 0.1C, and discharge termination voltage of 3.00V (vsLi + Under the condition of / Li), the charging capacity (mAh / g) after float charging was measured, and the capacity retention rate (%) after float charging was calculated by [charging capacity after float charging (mAh / g)] / [initial charging capacity (mAh / g)] × 100.

[0071] The results of each evaluation are shown in Table 1.

[0072] [Table 1]

[0073] From Examples 1-4 and Comparative Example 1 in Table 1, it can be seen that coating the conductive material with a lithium compound as a coating material suppresses the decomposition of the sulfide solid electrolyte and improves battery performance. Furthermore, it can be seen that heating the coating material to a predetermined temperature based on its melting point or decomposition temperature further suppresses the decomposition of the sulfide solid electrolyte. [Explanation of symbols]

[0074] 100 Sulfide solid state battery 110 Conductive composite material for sulfide solid state batteries 111 Conductive material 112 Covering material 120 Sulfide solid electrolyte 130 Cathode active material 140 Coating material for positive electrode active material

Claims

1. It has a conductive material and a coating material covering the surface of the conductive material, and The coating material is a lithium compound. Conductive composite material for sulfide solid state batteries.

2. The conductive composite material for a battery according to claim 1, wherein the coating material is selected from lithium carbonate, lithium hexafluoride phosphate, lithium chloride, lithium tetrafluoroborate, lithium phosphate, and lithium niobate, and combinations thereof.

3. A positive electrode active material layer for a sulfide solid battery, comprising the conductive composite material for a sulfide solid battery, a positive electrode active material, and a sulfide solid electrolyte as described in claim 1.

4. A coating material is applied to the surface of the conductive material, and Heat the coating material until its temperature reaches [(melting point or decomposition temperature of the coating material) - 120]°C or higher. including and The coating material is a lithium compound. A method for manufacturing conductive composite materials for sulfide solid-state batteries.

5. The method according to claim 4, wherein the coating material is selected from lithium carbonate, lithium hexafluoride phosphate, lithium chloride, lithium tetrafluoroborate, lithium phosphate, and lithium niobate, and combinations thereof.

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