All-solid-state battery and manufacturing method thereof

Abstract

The invention relates to an all-solid-state battery and a manufacturing method thereof. More specifically, in an all-solid-state battery according to the present invention, the structural stability is improved by ensuring the same cross-sectional shape and area of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in a unit cell in which the positive electrode layer, the solid electrolyte layer, and the negative electrode layer are stacked. And the porosity is reduced by containing sulfide-based solid electrolyte particles having different particle sizes inside the positive electrode active material layer, thereby improving the performance of the battery.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0157946, filed on November 15, 2023, and Korean Patent Application No. 10-2024-0157108, filed on November 7, 2024, the disclosures of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to an all-solid-state battery and a method for manufacturing the same. Background Art

[0004] Various batteries are being researched to overcome the limitations of current lithium secondary batteries in terms of capacity, safety, output, upsizing, and miniaturization.

[0005] Representative examples include metal-air batteries, which have a much higher theoretical capacity than lithium secondary batteries; all-solid-state batteries, which are safe and have no explosion risk; supercapacitors, which are powerful in terms of output; NaS batteries or redox flow batteries (RFBs) for large-scale applications; and thin-film batteries for miniaturization. Research into these technologies is ongoing in both academia and industry.

[0006] All-solid-state batteries replace the liquid electrolyte used in conventional lithium secondary batteries with a solid electrolyte. Because they do not use flammable solvents, they eliminate the potential for ignition or explosion caused by decomposition reactions of conventional electrolytes, significantly improving safety. They also offer the advantage of being able to use lithium metal or lithium alloys as the negative electrode material, significantly increasing energy density relative to battery mass and volume.

[0007] However, achieving precise alignment during the battery assembly process for all-solid-state batteries, where each electrode is stacked sequentially on top of a pouch, remains a challenge. When stacking cells to increase energy density, these misaligned cells create an unstable stack that can lead to cracks and short circuits.

[0008] Figures 1a to 1d Schematic diagram showing a longitudinal cross-section of an all-solid-state battery of the prior art (1a: longitudinal cross-section of a unit cell, 1b: longitudinal cross-section of a stacked cell, 1c: longitudinal cross-section of a laminate comprising a positive electrode layer and a solid electrolyte layer, 1d: enlarged view of the positive electrode layer and the solid electrolyte layer).

[0009] The unit cell 100 of the all-solid-state battery of the prior art has a structure in which a positive electrode current collector 111, a positive electrode active material layer 112, a solid electrolyte layer 120 and a negative electrode layer 130 are stacked in sequence ( Figure 1aThe stacked cell 200 is formed by stacking a plurality of unit cells 100, for example, two unit cells 100 are stacked together ( Figure 1b When manufacturing the unit cell 100, the area of ​​the positive electrode layer 110 including the positive electrode current collector 111 and the positive electrode active material layer 112 is smaller than that of the adjacent solid electrolyte layer 120, so it is not easy to align the solid electrolyte layer 120 on the positive electrode layer 110, which may cause misalignment ( Figure 1c Typically, the positive electrode layer is designed to be smaller than the solid electrolyte layer used as a separator because a short circuit would occur if the positive electrode layer stretched and contacted the negative electrode layer, or if the two electrode layers were misaligned during assembly. Furthermore, after stacking the components, cracks C may form in the solid electrolyte layer 120 due to a step difference caused by the area mismatch between the adjacent positive electrode active material layer 112 and solid electrolyte layer 120 during pressurization. If the stacked structure itself collapses D, contact between the positive and negative electrode layers may occur.

[0010] In addition, the positive electrode active material layer 112 includes a positive electrode active material, solid electrolyte particles, a binder, and a conductive material, and the energy density may be reduced due to pores formed between the particles, or the conductivity may be reduced due to the lack of contact at the interface of the positive electrode active material layer 112 and the solid electrolyte layer 120 ( Figure 1d ).

[0011] Figure 2 This is the structure of the all-solid-state battery disclosed in Korean Patent Application No. 2022-0080930.

[0012] Reference Figure 2 , it can be seen that a spacer 50 made of a polymer is provided in the space formed by the area of ​​the negative electrode layer 40 being smaller than the area of ​​the solid electrolyte layer 30 to ensure the structural stability of the all-solid-state battery. The spacer 50 is made of a polymer, and the polymer contains at least one selected from the group consisting of polyethylene, polyethylene naphthalate, polyethylene terephthalate, and a combination thereof. Since the spacer 50 is made of a different material from the negative electrode layer, when pressure is applied during the pressurization process in the manufacture of the all-solid-state battery, even if the negative electrode layer remains intact under the same pressure, cracks may be generated in the spacer 50 and the solid electrolyte layer 30 under load. This phenomenon is even more obvious in stacked cells.

[0013] Therefore, for the high stability of all-solid-state batteries, it is necessary to develop technologies that can easily achieve continuous alignment during the battery assembly process to ensure structural stability while preventing non-contact at the junction between the cathode layer and the solid electrolyte layer.

[0014] [Prior art literature]

[0015] (Patent Document 1) Korean Patent Application No. 2022-0080930 Summary of the Invention

[0016] [Technical Issues]

[0017] The inventors of the present disclosure have conducted various studies to solve the above-mentioned problems and confirmed that in an all-solid-state battery including a unit cell or a stacked cell in which a plurality of unit cells are stacked, the structural stability of the all-solid-state battery can be ensured by forming a unit cell including a positive electrode layer, a solid electrolyte layer and a negative electrode layer while designing the cross-sectional shape and area of ​​the positive electrode layer, the solid electrolyte layer and the negative electrode layer to be the same.

[0018] In addition, it was found that by including sulfide-based solid electrolyte particles with different particle sizes inside the positive electrode active material layer contained in the positive electrode layer, the porosity of the positive electrode active material layer was reduced, thereby improving the energy density of the battery, and the conductivity was improved by preventing the non-contact at the junction of the positive electrode layer and the solid electrolyte layer, thereby improving the performance of the battery.

[0019] Therefore, an object of the present disclosure is to provide an all-solid-state battery having structural stability and improved battery performance and a method for manufacturing the same.

[0020] [Technical solution]

[0021] In order to achieve the above object, the present disclosure provides an all-solid-state battery, which includes a unit cell,

[0022] Wherein, the unit cell includes:

[0023] positive electrode current collector;

[0024] a positive electrode active material layer, the positive electrode active material layer being in contact with a specific area on one surface of the positive electrode current collector;

[0025] a solid electrolyte layer surrounding one surface and adjacent side surfaces of the positive electrode active material layer and formed in contact with the positive electrode current collector; and

[0026] a negative electrode layer, the negative electrode layer being located on the solid electrolyte layer and having an area equal to that of the solid electrolyte layer,

[0027] The positive electrode active material layer comprises a positive electrode active material, a binder, a conductive material and sulfide-based solid electrolyte particles.

[0028] The sulfide-based solid electrolyte particles include first sulfide-based solid electrolyte particles and second sulfide-based solid electrolyte particles, and the particle size of the second sulfide-based solid electrolyte particles is smaller than that of the first sulfide-based solid electrolyte particles.

[0029] In one example of the present invention, the concentration of the second sulfide-based solid electrolyte particles may increase from the center toward the surface of the positive electrode active material layer.

[0030] In one example of the present disclosure, an all-solid-state battery is provided, wherein the area of ​​the solid electrolyte layer is 1.3 to 1.8 times the area of ​​the positive electrode active material layer.

[0031] In one example of the present disclosure, the porosity of the positive electrode active material layer may be 8% to 15%.

[0032] In one example of the present disclosure, an all-solid-state battery is provided, wherein the negative electrode layer includes: a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector, wherein the negative electrode active material layer can be stacked to contact the solid electrolyte layer.

[0033] In one example of the present disclosure, an all-solid-state battery is provided, wherein the negative electrode layer includes: a negative electrode current collector; and an anode-free coating layer formed on the negative electrode current collector, wherein the anode-free coating layer may be stacked to contact the solid electrolyte layer.

[0034] In one example of the present disclosure, an all-solid-state battery is provided, in which two or more unit cells are stacked.

[0035] In one example of the present invention, the present disclosure provides an all-solid-state battery, wherein the all-solid-state battery is a pouch type.

[0036] The present invention provides a method for manufacturing an all-solid-state battery, which includes a unit cell manufacturing process, wherein the unit cell manufacturing process includes the following steps:

[0037] (S1) forming a positive electrode active material layer of a specific area on a positive electrode current collector;

[0038] (S2) forming a solid electrolyte layer on the positive electrode active material layer so as to surround one surface and adjacent side surfaces of the positive electrode active material layer;

[0039] (S3) forming a negative electrode layer on the solid electrolyte layer with an area equal to that of the solid electrolyte layer; and

[0040] (S4) pressurizing and joining the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode layer in a stacking direction,

[0041] The positive electrode active material layer contained in the manufactured all-solid-state battery comprises a positive electrode active material, a binder, a conductive material and sulfide-based solid electrolyte particles.

[0042] The sulfide-based solid electrolyte particles include first sulfide-based solid electrolyte particles and second sulfide-based solid electrolyte particles, and the particle size of the second sulfide-based solid electrolyte particles is smaller than that of the first sulfide-based solid electrolyte particles.

[0043] In one example of the present disclosure, a method for manufacturing an all-solid-state battery is provided, wherein the pressure is 300 MPa to 700 MPa.

[0044] In one example of the present disclosure, a method for manufacturing an all-solid-state battery is provided, wherein the positive electrode active material layer in step (S1) contains first sulfide-based solid electrolyte particles, and during the formation of the solid electrolyte layer in step (S2), when a slurry for forming the solid electrolyte layer is applied, a portion of the second sulfide-based solid electrolyte particles contained in the slurry is injected into the positive electrode active material layer.

[0045] [Beneficial Effects]

[0046] The all-solid-state battery disclosed herein comprises a unit cell having a structure in which a positive electrode layer, a solid electrolyte layer and a negative electrode layer are stacked in sequence, wherein the positive electrode layer, the solid electrolyte layer and the negative electrode layer have the same shape and cross-section, thereby achieving structural stability, so that damage such as cracking and stretching can be prevented even during the pressurization and joining process during manufacturing.

[0047] Furthermore, in order to increase energy density, when two or more unit cells are stacked to form a stacked cell, the unit cells may also exhibit structural stability, which may exhibit excellent lifespan characteristics.

[0048] In addition, including sulfide-based solid electrolyte particles of different particle sizes in the positive electrode active material layer can reduce pores, which can improve battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figures 1a to 1d Schematic diagram showing a longitudinal cross-section of an all-solid-state battery of the prior art (1a: longitudinal cross-section of a unit cell, 1b: longitudinal cross-section of a stacked cell, 1c: longitudinal cross-section of a laminate comprising a positive electrode layer and a solid electrolyte layer, 1d: enlarged view of the positive electrode layer and the solid electrolyte layer).

[0050] Figure 2 This is the structure of the all-solid-state battery disclosed in Korean Patent Application No. 2022-0080930.

[0051] Figures 3a to 3e3a: longitudinal cross-section of a unit cell, 3b: longitudinal cross-section of a stacked cell, 3c: longitudinal cross-section of a laminate comprising a positive electrode layer and a solid electrolyte layer, 3d: enlarged view of the longitudinal cross-section of the positive electrode layer and the solid electrolyte layer, 3e: scanning electron microscope photograph (SEM) of the longitudinal cross-section of the positive electrode layer and the solid electrolyte layer.

[0052] Figures 4a to 4d It is a schematic diagram of the unit cell manufacturing process of Example 1 of the present embodiment (4a: setting of the positive electrode, 4b: manufacturing of the solid electrolyte layer, 4c: top view and longitudinal view of the manufactured solid electrolyte layer, 4d: cutting of the stack including the positive electrode layer and the solid electrolyte layer, 4e: schematic diagram of injecting second sulfide-based solid electrolyte particles into the positive electrode active material layer from the slurry for forming the solid electrolyte layer).

[0053] Figure 5 These are scanning electron microscope photographs of cross sections of the positive electrodes of Example 1 and Comparative Example 1.

[0054] Figure 6 Graph showing the performance evaluation results of the all-solid-state batteries manufactured in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0055] Hereinafter, the present invention will be described in more detail to provide a better understanding.

[0056] The terms and words used in this specification and claims should not be interpreted with their ordinary or dictionary meanings, but rather are given the principle that the inventor can define the concepts of the terms that he / she considers most suitable to describe his / her invention, with meanings and concepts consistent with the technical idea of ​​the present invention.

[0057] All-solid-state batteries

[0058] The present disclosure relates to an all-solid-state battery.

[0059] The all-solid-state battery of the present invention comprises a unit cell,

[0060] Wherein, the unit cell includes:

[0061] positive electrode current collector;

[0062] a positive electrode active material layer, the positive electrode active material layer being in contact with a specific area on one surface of the positive electrode current collector;

[0063] a solid electrolyte layer surrounding one surface and adjacent side surfaces of the positive electrode active material layer and formed in contact with the positive electrode current collector; and

[0064] a negative electrode layer, the negative electrode layer being located on the solid electrolyte layer and having an area equal to that of the solid electrolyte layer,

[0065] The positive electrode active material layer comprises a positive electrode active material, a binder, a conductive material and sulfide-based solid electrolyte particles.

[0066] The sulfide-based solid electrolyte particles include first sulfide-based solid electrolyte particles and second sulfide-based solid electrolyte particles, and the particle size of the second sulfide-based solid electrolyte particles is smaller than that of the first sulfide-based solid electrolyte particles.

[0067] Since the all-solid-state battery of the present invention does not contain any foreign materials except the positive electrode layer, the solid electrolyte layer and the negative electrode layer, problems such as structural instability and battery performance degradation caused by the addition of foreign materials can be avoided.

[0068] Therefore, a unit cell of an all-solid-state battery may include a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

[0069] Figures 3a to 3e 3a: longitudinal cross-section of a unit cell, 3b: longitudinal cross-section of a stacked cell, 3c: longitudinal cross-section of a laminate comprising a positive electrode layer and a solid electrolyte layer, 3d: enlarged view of the longitudinal cross-section of the positive electrode layer and the solid electrolyte layer, 3e: scanning electron microscope photograph (SEM) of the longitudinal cross-section of the positive electrode layer and the solid electrolyte layer.

[0070] Reference Figures 3a to 3d The unit cell 100 included in the all-solid-state battery has a structure in which a positive electrode current collector 111, a positive electrode active material layer 112, a solid electrolyte layer 120 and a negative electrode layer 130 are stacked in sequence.

[0071] The positive electrode active material layer 112 contacts one surface of the positive electrode current collector 111, but contacts a specific area of ​​the surface. In the positive electrode active material layer 112, the other surface other than the one in contact with the positive electrode current collector 111 and the four side surfaces adjacent to the other surface are surrounded by the solid electrolyte layer 120. In the positive electrode active material layer 112, the one surface in contact with the positive electrode current collector 111 can be referred to as the first surface, the other surface can be referred to as the second surface, and the four side surfaces adjacent to the first and second surfaces can be referred to as the first side surface, the second side surface, the third side surface, and the fourth side surface.

[0072] The unit cell 100 or the stacked cell 200 may have a rectangular parallelepiped shape, in which the cross-sections of the positive electrode current collector 111, the solid electrolyte layer 120, and the negative electrode layer 130 have the same area and shape. In addition, in the portion of the positive electrode active material layer 112 surrounded by the solid electrolyte layer 120 on the side, the area and shape of the cross-section of the positive electrode active material layer 112 plus the cross-section of the solid electrolyte layer 120 may be the same as the area and shape of the positive electrode current collector 111 ( Figure 3a and 3b ).

[0073] Since the unit cell 100 has a rectangular parallelepiped shape and a stable structure, the unit cell 100 is more easily aligned during the manufacture of the unit cell 100, and the problem of the unit cell 100 being stacked and then pressurized as described above is avoided. Figure 3c ) such as cracking, stretching or cell shortening.

[0074] In addition, refer to Figure 3e As can be seen from the SEM photograph of , the solid electrolyte layer 120 is formed by overcoating the positive electrode active material layer 112. When the battery is charged or discharged, lithium ions can also move through the solid electrolyte formed on the side of the positive electrode active material layer, which improves ion conductivity.

[0075] In one example of the present disclosure, the positive electrode layer includes a positive electrode current collector and a positive electrode active material layer formed on one surface of the positive electrode current collector.

[0076] The positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between the external wiring and the positive electrode active material layer.

[0077] In addition, the positive electrode current collector is not particularly limited as long as it has high electronic conductivity and does not cause chemical changes in the all-solid-state battery. As the positive electrode current collector, for example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, or copper or stainless steel with a carbon, nickel or silver surface treatment, aluminum-cadmium alloy, etc. can be used.

[0078] In addition, the positive electrode current collector may have a fine concave-convex structure on its surface, or may adopt a three-dimensional porous structure to enhance the bonding force with the positive electrode active material layer. Therefore, the positive electrode current collector may include various forms, such as films, sheets, foils, meshes, nets, porous materials, foams, non-woven materials, etc.

[0079] The positive electrode active material layer may have an area smaller than that of the positive electrode current collector and be located on the positive electrode current collector.

[0080] In one example of the present disclosure, the positive electrode active material layer includes a positive electrode active material, a binder, a conductive material, and sulfide-based solid electrolyte particles.

[0081] The sulfide-based solid electrolyte particles contained in the positive electrode active material layer include first sulfide-based solid electrolyte particles (P1) and second sulfide-based solid electrolyte particles (P2) having a smaller particle size than the first sulfide-based solid electrolyte particles (P1) ( Figure 3d ).

[0082] The particle size of the second sulfide-based solid electrolyte particles is smaller than that of the first sulfide-based solid electrolyte particles, and the particle size range is not particularly limited as long as it is sufficient to fill the pores of the positive electrode active material layer. For example, the particle size of the second sulfide-based solid electrolyte particles can be 0.1 to 2 μm, and the particle size of the first sulfide-based solid electrolyte particles can be 2 to 6 μm. In this case, the particle size is the length of the longest axis of the particle.

[0083] Alternatively, the concentration of the second sulfide-based solid electrolyte particles may increase from the center toward the surface of the positive electrode active material layer. In this case, concentration may refer to the distribution of particles, and an increase in concentration from the center toward the surface of the positive electrode active material layer means that the sulfide-based solid electrolyte particles are distributed on the surface in a relatively large amount. Therefore, concentration can indicate density.

[0084] During the manufacturing process, when the solid electrolyte layer-forming slurry is applied to the positive electrode active material layer, the second sulfide-based solid electrolyte particles are injected into the positive electrode active material layer. Therefore, the second sulfide-based solid electrolyte particles are more densely distributed closer to the surface of the positive electrode active material layer adjacent to the solid electrolyte layer.

[0085] In addition, the porosity of the positive electrode active material layer may be 8% to 15%. The porosity refers to the porosity when the positive electrode active material layer contains both the first sulfide-based solid electrolyte particles and the second sulfide-based solid electrolyte particles.

[0086] The injection of the second sulfide-based solid electrolyte particles, which have a smaller particle size than the first sulfide-based solid electrolyte particles, fills the pores formed between the positive electrode active material, binder, conductive material, and the first sulfide-based solid electrolyte particles, thereby reducing the porosity of the positive electrode active material layer. This reduced porosity in the positive electrode active material layer can increase energy density and improve battery performance. Furthermore, before the injection of the second sulfide-based solid electrolyte particles, that is, when only the first sulfide-based solid electrolyte particles are included in the first and second sulfide-based solid electrolyte particles in the positive electrode active material layer, the porosity can be 15% to 25%.

[0087] In addition, based on the total weight of the positive electrode active material layer, the content of the sulfide-based solid electrolyte particles may be 5% to 40% by weight. Specifically, the content of the sulfide-based solid electrolyte particles may be 5% by weight or more, 10% by weight or more, or 15% by weight or more, and 25% by weight or less, 35% by weight or less, or 40% by weight or less. If the content of the sulfide-based solid electrolyte particles is less than 5% by weight, the ion conductivity enhancement effect may not be significant, and if it is greater than 40% by weight, the content of the positive electrode active material, binder or conductive material may be relatively reduced, resulting in a decrease in battery performance.

[0088] Furthermore, the first sulfide-based solid electrolyte particles and / or the second sulfide-based solid electrolyte particles may include a compound represented by the following Formula 1 or a mixture thereof:

[0089] <Formula 1>

[0090] Li a M b S c X d

[0091] wherein M is selected from P, Sn, Sb, As and Ge;

[0092] wherein X is selected from Cl, Br and I,

[0093] 5≤a≤7.5,0.5 <b≤1.5,4<c≤6,0.5<d≤2。

[0094] The first sulfide-based solid electrolyte particles and the second sulfide-based solid electrolyte particles may be the same or different insofar as they include the compound represented by Formula 1 or a mixture thereof.

[0095] In addition, the positive electrode active material may be any material that can reversibly absorb and release lithium ions, but is not particularly limited, for example, layered compounds such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), Li[Ni x Co y Mn z M v ]O2 (wherein M is any one or more elements selected from the group consisting of Al, Ga and In, and 0.3≤x<1.0, 0≤y, z≤0.5, 0≤v≤0.1, x+y+z+v=1), Li(Li a M b-a-b' M' b' )O 2-c A c(wherein 0≤a≤0.2, 0.6≤b≤1, 0≤b'≤0.2 and 0≤c≤0.2; M comprises at least one selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn and Ti; M' comprises at least one selected from the group consisting of Al, Mg and B; and A comprises at least one selected from the group consisting of P, F, S and N) or a compound substituted with one or more transition metals; lithium manganese oxide, such as Li 1+y Mn 2-y Compounds of LiMnO4 (wherein y is 0 to 0.33), LiMnO3, LiMn2O3 or LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5 or Cu2V2O7; compounds of the formula LiNi 1-y M y Ni-type lithium nickel oxide represented by O2 (wherein M is Co, Mn, Al, Cu, Fe, Mg, B or Ga, and y is 0.01 to 0.3; represented by the formula LiMn 2-y M y Lithium manganese composite oxide represented by Li2Mn3MO8 (wherein M is Co, Ni, Fe, Cr, Zn or Ta, and y is 0.01 to 0.1); LiMn2O4, wherein a portion of Li in the formula is replaced by alkaline earth metal ions; disulfide; Fe2(MoO4)3, etc., but not limited thereto.

[0096] In addition, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material may be 60% to 90% by weight. Specifically, the content of the positive electrode active material may be 60% by weight, 65% by weight or more, or 70% by weight or more, 80% by weight or less, 85% by weight or less, or 90% by weight or less. If the content of the positive electrode active material is less than 60% by weight, battery performance may be reduced, and if the content is greater than 90% by weight, mass transfer resistance may increase.

[0097] In addition, the conductive material is not particularly limited as long as it can prevent side reactions in the internal environment of the all-solid-state battery and has excellent electronic conductivity without causing chemical changes in the battery. As a representative, graphite or conductive carbon can be used, for example, graphite such as natural graphite, artificial graphite, etc.; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, summer black, etc.; carbon-based materials having a graphene or graphite crystal structure; conductive fibers such as carbon fibers, metal fibers, etc.; carbon fluorides; metal powders such as aluminum powder, nickel powder, etc.; conductive whiskers such as zinc oxide, potassium titanate, etc.; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; and they can be used alone or in a mixture of two or more of the above, but are not necessarily limited thereto. Preferably, the conductive material may include vapor grown carbon fibers (VGCF).

[0098] Based on the total weight of the positive electrode active material layer, the content of the conductive material can generally be 0.1 wt % to 5 wt %, more specifically, the content of the conductive material can be 0.1 wt % or more, 0.5 wt % or more, 1 wt % or more, 1.5 wt % or more, 2 wt % or more, 4 wt % or less, 4.5 wt % or less, or 5 wt % or less. If the content of the conductive material is too little, for example, less than 0.1 wt %, it is difficult to expect the effect of improving conductivity or the electrochemical properties of the battery may deteriorate, and if it is too much, for example, greater than 5 wt %, the amount of the positive electrode active material may be relatively small, resulting in a reduction in capacity and energy density. There is essentially no limitation on the method for incorporating the conductive material into the positive electrode, and any conventional method known in the art can be used, such as mixing with the positive electrode active material or coating the positive electrode active material.

[0099] The binder is a component that helps to bind the positive electrode active material to the conductive material or to the current collector, and may include at least one selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinyl pyrrolidone, polyvinyl pyridine, poly Vinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride and poly (vinylidene fluoride) - hexafluoropropylene polymer. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0100] In addition, based on the total weight of the positive electrode active material layer, the content of the binder may be 0.5 wt % to 4 wt %, and more specifically, the content of the binder may be 0.5 wt % or more, 1 wt % or more, 1.5 wt % or more, 3 wt % or less, 3.5 wt % or less, or 4 wt % or less. If the binder content is less than 0.5 wt %, the adhesion between the positive electrode active material and the positive electrode current collector may be reduced. If the binder content is greater than 4 wt %, the adhesion may be improved, but the content of the positive electrode active material may be reduced, resulting in a reduction in the battery cell capacity.

[0101] In one embodiment of the present disclosure, the solid electrolyte layer may be 1.3 to 1.8 times the area of ​​the positive electrode active material layer. Here, the areas of the solid electrolyte layer and the positive electrode active material layer refer to the areas when the solid electrolyte layer and the positive electrode active material layer are viewed from above.

[0102] The solid electrolyte layer is formed to wrap around one surface of the positive electrode active material layer and the adjacent side surfaces, so that the area of ​​the solid electrolyte layer is larger than that of the positive electrode active material layer. If the area of ​​the solid electrolyte layer is less than 1.3 times that of the positive electrode active material, a step difference may occur between the solid electrolyte layer and the positive electrode current collector or negative electrode layer. If it exceeds 1.8 times, the lithium ion migration path may become longer or manufacturing costs may increase.

[0103] Furthermore, the solid electrolyte layer may include sulfide-based solid electrolyte particles.

[0104] The sulfide-based solid electrolyte particles may include a compound represented by the following Formula 1 or a mixture thereof:

[0105] <Formula 1>

[0106] Li a M b S c X d

[0107] wherein M is selected from P, Sn, Sb, As and Ge;

[0108] wherein X is selected from Cl, Br and I,

[0109] 5≤a≤7.5,0.5 <b≤1.5,4<c≤6,0.5<d≤2。

[0110] The sulfide-based solid electrolyte particles contained in the solid electrolyte layer may be the same as the second sulfide-based solid electrolyte particles contained in the positive electrode active material layer. During the manufacturing process, the second sulfide-based solid electrolyte particles contained in the solid electrolyte layer-forming slurry may also be injected into the positive electrode active material layer.

[0111] In one example of the present disclosure, a negative electrode layer includes: a negative electrode current collector; and a negative electrode active material layer formed on the negative electrode current collector, wherein the negative electrode active material layer may be stacked to contact a solid electrolyte layer.

[0112] Alternatively, the negative electrode layer may include: a negative electrode current collector; and an anode-free coating layer formed on the negative electrode current collector, wherein the anode-free coating layer is stacked to contact the solid electrolyte layer.

[0113] The negative electrode active material layer includes a negative electrode active material, a binder, and a conductive material.

[0114] The negative electrode active material may include a material capable of reversibly inserting or deinserting lithium (Li + ) material, a material capable of reacting with lithium ions to reversibly form a lithium-containing compound, lithium metal or a lithium alloy.

[0115] Able to reversibly insert or deinsert lithium ions (Li + ) can be, for example, crystalline carbon, amorphous carbon or a mixture thereof. + ) to reversibly form a lithium-containing compound may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of indium (In), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al), and tin (Sn).

[0116] Preferably, the negative electrode active material may be lithium metal or lithium-indium alloy (Li-In), and more specifically, may be in the form of lithium metal or lithium thin film, or lithium-indium alloy thin film or powder.

[0117] The content of the negative electrode active material may be 40 to 80% by weight based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40% by weight or more, or 50% by weight or more, or 70% by weight or less, or 80% by weight or less. If the content of the negative electrode active material is less than 40% by weight, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if the content is greater than 80% by weight, the mass transfer resistance may be greater.

[0118] The binder is a component that helps to bind the negative electrode active material to the conductive material or to the negative electrode current collector, and may include at least one selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinyl pyrrolidone, polyvinyl pyridine, Polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenolic resin, epoxy resin, carboxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride and poly (vinylidene fluoride) - hexafluoropropylene polymer. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0119] In addition, the content of the binder may be 0.5 wt % to 4 wt % based on the total weight of the negative electrode active material layer. More specifically, the content of the binder may be 0.5 wt % or more, 1 wt % or more, 1.5 wt % or more, or 3 wt % or less, 3.5 wt % or less, or 4 wt % or less. If the binder content is less than 0.5 wt %, the adhesion between the positive electrode active material and the negative electrode current collector may be reduced. If the binder content is greater than 4 wt %, the adhesion may be improved, but the content of the negative electrode active material may be reduced, resulting in a reduced battery capacity.

[0120] In addition, the above-mentioned conductive material is not particularly limited, as long as it can prevent side reactions in the internal environment of the all-solid-state battery and has excellent electronic conductivity without causing chemical changes in the battery. As a representative, graphite or conductive carbon can be used, for example, graphite, such as natural graphite, artificial graphite, etc.; carbon black, such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, summer black, etc.; carbon-based materials with graphene or graphite crystal structure; conductive fibers, such as carbon fibers, metal fibers, etc.; carbon fluorides; metal powders, such as aluminum powder, nickel powder, etc.; conductive whiskers, such as zinc oxide, potassium titanate, etc.; conductive oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives; and they can be used alone or in a mixture of two or more of the above, but are not necessarily limited thereto. Preferably, the conductive material may include vapor grown carbon fibers (VGCF).

[0121] Based on the total weight of the negative electrode active material layer, the content of the conductive material can generally be 0.1 wt % to 5 wt %, more specifically, the content of the conductive material can be 0.1 wt % or more, 0.5 wt % or more, 1 wt % or more, 1.5 wt % or more, 2 wt % or more, 4 wt % or less, 4.5 wt % or less, or 5 wt % or less. If the content of the conductive material is too little, for example, less than 0.1 wt %, it is difficult to expect the effect of improving conductivity or the electrochemical properties of the battery may deteriorate, and if it is too much, for example, greater than 5 wt %, the amount of the negative electrode active material may be relatively small, resulting in a decrease in capacity and energy density. There is essentially no limitation on the method for incorporating the conductive material into the negative electrode, and any conventional method known in the art, such as mixing with the negative electrode active material or coating the negative electrode active material, can be used.

[0122] In addition, the negative electrode current collector is not particularly limited as long as it has conductivity and does not cause chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with a surface treated with carbon, nickel or silver, aluminum-cadmium alloy, etc. can be used. In addition, like the positive electrode current collector, the negative electrode current collector can be in various forms with fine concave and convex structures formed on the surface, such as a film, sheet, foil, mesh, porous material, foam, non-woven material, etc.

[0123] The manufacturing method of the negative electrode is not particularly limited and can be manufactured by forming a negative electrode active material layer on the negative electrode current collector using a conventional layer or film formation method. For example, methods such as pressing, coating, or deposition can be used. The negative electrode of the present invention also includes the case where a metallic lithium thin film is formed on the metal plate by initial charging after assembling the battery without a lithium thin film on the negative electrode current collector.

[0124] In addition, the non-anodic coating does not contain negative electrode active material, and negative electrode active material may be formed in the non-anodic coating during charging. For example, when the battery is charged, lithium ions may be displaced from the positive electrode, causing lithium metal to precipitate from the negative electrode. In other words, the non-anodic coating may be a film that induces lithium precipitation.

[0125] The non-anodic coating layer may include metal particles and carbon material particles, and more specifically, may include a carbon material-metal composite material.

[0126] The carbon material particles can be, for example, amorphous carbon material particles. However, the carbon material particles are not limited to amorphous particles. Specific examples of amorphous carbon materials can include carbon black (such as acetylene black, furnace black and Ketjen black), graphene or a combination thereof.

[0127] In addition, the metal particles may form an alloy with lithium, and the metal particles may be one or more particles selected from silver (Ag), gold, platinum, palladium, silicon, aluminum, bismuth, tin, indium, and zinc. The non-anodic coating may be formed as a very thin film having a small thickness, for example, a thickness of 10 μm or less.

[0128] Preferably, the anode-free coating layer may include an Ag—C composite material as a carbon material-metal composite material, and lithium may be precipitated between the negative electrode current collector and the coating layer including the Ag—C composite material during the first charge.

[0129] In one example of the present invention, two or more unit cells may be stacked to produce a stacked cell.

[0130] Since the unit cell has a rectangular parallelepiped shape, even if two or more unit cells are stacked, they still have a rectangular parallelepiped shape, and the stacked cells can have structural stability.

[0131] In one example of the present disclosure, the all-solid-state battery may be a pouch-type all-solid-state battery.

[0132] Manufacturing method of all-solid-state battery

[0133] The present disclosure also relates to a method for manufacturing an all-solid-state battery.

[0134] The manufacturing method of the all-solid-state battery of the present invention includes a unit cell manufacturing process, and the unit cell manufacturing process includes the following steps (S1) to (S4):

[0135] (S1) forming a positive electrode active material layer of a specific area on a positive electrode current collector;

[0136] (S2) forming a solid electrolyte layer on the positive electrode active material layer so as to surround one surface and adjacent side surfaces of the positive electrode active material layer;

[0137] (S3) forming a negative electrode layer on the solid electrolyte layer with an area equal to that of the solid electrolyte layer; and

[0138] (S4) The positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode layer are pressurized and joined in a stacking direction.

[0139] The positive electrode active material layer contained in the unit cells joined after pressurization in step ( S4 ) contains a positive electrode active material, a binder, a conductive material, and sulfide-based solid electrolyte particles.

[0140] The sulfide-based solid electrolyte particles may include first sulfide-based solid electrolyte particles and second sulfide-based solid electrolyte particles having a particle size smaller than a particle size of the first sulfide-based solid electrolyte particles.

[0141] Hereinafter, each step of the method for manufacturing the all-solid-state battery of the present disclosure will be described in more detail.

[0142] In one example of the present disclosure, in step ( S1 ), a positive electrode active material layer having a specific area may be formed on a positive electrode current collector.

[0143] The area of ​​the positive electrode current collector can be larger than the area of ​​the positive electrode active material layer. The area of ​​the positive electrode current collector can be 1.3 to 1.8 times the area of ​​the positive electrode active material layer. The area of ​​the positive electrode current collector can be the same as the area of ​​the solid electrolyte layer, which may be advantageous for manufacturing a unit cell with a rectangular parallelepiped shape.

[0144] The positive electrode active material layer can be prepared as follows: a positive electrode active material layer-forming composition prepared by mixing a positive electrode active material, a solid electrolyte, a conductive material, and a binder in an organic solvent is applied to a positive electrode current collector and dried, and the positive electrode current collector is optionally compression-molded to increase the electrode density. In this case, it is preferred to use an organic solvent that can uniformly disperse the positive electrode active material, solid electrolyte, binder, and conductive material and easily evaporate. Specifically, examples include acetonitrile, methanol, ethanol, xylene, toluene, hexane, tetrahydrofuran, water, and isopropanol.

[0145] The sulfide-based solid electrolyte contained in the positive electrode active material layer formed in step ( S1 ) may be a first sulfide-based solid electrolyte.

[0146] In one example of the present disclosure, in step (S2), a solid electrolyte layer may be formed on the positive electrode active material layer to surround one surface and adjacent side surfaces of the positive electrode active material layer. In the positive electrode active material layer, one surface in contact with the positive electrode current collector is referred to as a first surface, the other surface is referred to as a second surface, and the four side surfaces adjacent to the first surface and the second surface are referred to as a first side surface, a second side surface, a third side surface, and a fourth side surface.

[0147] The solid electrolyte layer is formed on the positive electrode active material layer, surrounding the second surface and the first to fourth side surfaces of the positive electrode active material layer. Furthermore, because the area of ​​the positive electrode current collector is larger than that of the positive electrode active material layer, the solid electrolyte layer is formed even on the positive electrode current collector that is not in contact with the positive electrode active material layer.

[0148] The solid electrolyte layer can be prepared by applying a slurry obtained by mixing sulfide-based solid electrolyte particles and a binder in a solvent to the positive electrode active material layer, followed by drying. When the above-mentioned solid electrolyte layer-forming slurry is applied to the positive electrode active material layer, a portion of the second sulfide-based solid electrolyte particles contained in the slurry can also be injected into the positive electrode active material layer. The second sulfide-based solid electrolyte particles injected into the positive electrode active material layer can have a high concentration at the surface of the positive electrode active material layer. As a result, the concentration of the second sulfide-based solid electrolyte particles tends to increase from the center toward the surface of the positive electrode active material layer.

[0149] In addition, the binder resin may include at least one selected from the group consisting of acrylic copolymers, acrylic block copolymers, acrylic monomers, random copolymers of oligomers, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymers, acrylonitrile-butadiene rubber, nitrile rubber, acrylonitrile-styrene-butadiene copolymers, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene and ethylene / propylene copolymers.

[0150] In addition, 5 to 15 parts by weight of a binder may be included per 100 parts by weight of the solid electrolyte. Specifically, the content of the binder may be 5 parts by weight or more, 7 parts by weight or more, or 9 parts by weight or more, or 11 parts by weight or less, or 13 parts by weight or less, or 15 parts by weight or less. If the content of the binder is less than 5 parts by weight, it may be difficult to form a solid electrolyte layer, and if it exceeds 15 parts by weight, the ionic conductivity may be reduced.

[0151] In addition, the solvent is not particularly limited, as long as it is a solvent capable of dissolving and / or dispersing sulfide-based solid electrolyte particles and / or adhesive to form a slurry. For example, the solvent can be selected from at least one of the groups consisting of dimethyl sulfoxide (DMSO), isopropyl alcohol, ethyl butyrate, heptyl butyrate, hexyl butyrate, butyl butyrate, isopropyl butyrate, isobutyl isobutyrate, N-methyl pyrrolidone (NMP), acetone, toluene, xylene, N, N-dimethylformamide (DMF), benzene, tetrahydrofuran (THF) and water. The amount of the solvent used can be adjusted by considering the thickness of the coating, the properties of the prepared solid electrolyte, etc.

[0152] The coating method may be rod coating, roll coating, spin coating, slit coating, die coating, blade coating, comma coating, slot die coating, lip coating or solution casting, but is not limited thereto, as long as coating can form a layer.

[0153] There are no particular limitations on drying, as long as the drying method can evaporate the solvent after coating to form a layer. For example, drying can be performed at a temperature below 300°C. Specifically, the drying temperature can be below 300°C, below 200°C, below 150°C, or below 100°C.

[0154] In one example of the present disclosure, in step ( S3 ), the negative electrode layer having the same area as the solid electrolyte layer may be formed by laminating on the solid electrolyte layer.

[0155] In one example of the present disclosure, in step (S4), the positive electrode collector, the positive electrode active material layer, the solid electrolyte layer and the negative electrode layer can be joined by applying pressure in the stacking direction of the positive electrode collector, the positive electrode active material layer, the solid electrolyte layer and the negative electrode layer.

[0156] The pressure may be 300 MPa to 700 MPa, specifically, 300 MPa or more, 350 MPa or more, 400 MPa or more and 500 MPa or less, 550 MPa or less, 600 MPa or less, 650 MPa or less, or 700 MPa or less. If the pressure is less than 300 MPa, the internal adhesion of the all-solid-state battery may be poor, or the second sulfide-based solid electrolyte particles contained in the solid electrolyte layer may not be injected into the positive electrode active material layer. If the pressure is greater than 700 MPa, the positive electrode and electrolyte may rupture if they are not aligned.

[0157] The all-solid-state battery prepared by the above-mentioned manufacturing method has the same cross-sectional shape and area at any point in the stacked state of the positive electrode layer, the solid electrolyte layer and the negative electrode layer, thereby ensuring structural stability.

[0158] In addition, the positive electrode active material layer contained in the positive electrode layer can be configured to include first sulfide-based solid electrolyte particles and second sulfide-based solid electrolyte particles of different particle sizes, thereby reducing porosity and reducing the non-contact at the interface between the positive electrode active material layer and the solid electrolyte layer. This may increase the energy density of the all-solid-state battery and improve its performance.

[0159] Hereinafter, preferred embodiments of the present disclosure are described for the purpose of illustrating the present disclosure, but it will be apparent to those skilled in the art that various changes and modifications may be made within the scope of the present disclosure and technical ideas, and these changes and modifications fall within the scope of the appended claims.

[0160] Example 1

[0161] (1) Formation of the positive electrode layer

[0162] The positive electrode active material layer forming slurry is coated on the aluminum current collector and dried to form the positive electrode active material layer.

[0163] At this time, the slurry for forming the positive electrode active material layer is prepared by mixing and dispersing the positive electrode active material, first sulfide-based solid electrolyte particles, a binder, and a conductive material in an organic solvent. The positive electrode active material is lithium cobalt oxide (LiCoO2), the first sulfide-based solid electrolyte particles are sulfide-based solid electrolyte particles having an argyrodite structure, namely Li6PS5Cl, the conductive material is vapor-grown carbon fiber (VGCF), and the binder is polytetrafluoroethylene (PTFE).

[0164] In addition, a positive electrode active material layer is formed on a portion of one surface of the positive electrode current collector. In other words, the cross-sectional area of ​​the positive electrode active material layer is formed to be smaller than or equal to the cross-sectional area of ​​the positive electrode current collector.

[0165] (2) Manufacturing of battery cells

[0166] Figures 4a to 4d The present invention is a schematic diagram of the manufacturing process of a unit cell of Example 1 (4a: arrangement of the positive electrode, 4b: manufacture of the solid electrolyte layer, 4c: top view and longitudinal view of the manufactured solid electrolyte layer, 4d: cutting of the laminate including the positive electrode layer and the solid electrolyte layer, 4e: schematic diagram of injecting the second sulfide-based solid electrolyte particles from the solid electrolyte layer forming slurry into the positive electrode active material layer). The unit cell is manufactured as follows by coating the positive electrode layer prepared in (1) above according to the above manufacturing method.

[0167] The plurality of stamped positive electrode layers 110 are placed on a polyethylene terephthalate (PET) release film (RF) ( Figure 4aThen, the solid electrolyte layer (S) forming slurry ( Figure 4b ) and dried to form a solid electrolyte layer 120 ( Figure 4c The stack of the positive electrode layer and the solid electrolyte layer is cut into individual positive electrode layer units ( Figure 4d ). The solid electrolyte layer area is formed to be larger than the area of ​​the positive electrode active material layer contained in the positive electrode layer. The slurry for forming the solid electrolyte is prepared by mixing second sulfide-based solid electrolyte particles Li6PS5Cl having an argyrodite structure and having a smaller particle size than the first sulfide-based solid electrolyte particles, a binder, and a solvent. When the slurry (S) for forming the solid electrolyte layer is applied on the positive electrode layer 110, a portion of the second sulfide-based solid electrolyte particles (P2) contained in the slurry (S) can penetrate into the positive electrode active material layer 112 and fill the pores near the surface of the positive electrode active material layer 112, thereby reducing the porosity ( Figure 4e At this time, the area of ​​the positive electrode active material layer is set to A 2 mm 2 , the area of ​​the solid electrolyte layer is set to B 2 mm 2 When the positive electrodes are provided, the interval between the positive electrodes is set to C mm, and this process is performed in the manner of C<A<B, C=(BA).

[0168] Then, the negative electrode layer is stacked on top of the solid electrolyte layer and pressurized to 400 MPa to prepare a unit cell. After pressurization, the porosity within the positive electrode active material layer 112 can be further reduced, resulting in a denser positive electrode. In the unit cell, the area of ​​the positive electrode current collector contained in the positive electrode layer, the total area of ​​the positive electrode active material layer and the solid electrolyte layer surrounding the positive electrode active material layer, the area of ​​the solid electrolyte layer, and the area of ​​the negative electrode layer are the same. A stacked cell can be manufactured by stacking two of the above-mentioned unit cells.

[0169] The negative electrode layer is formed by laminating lithium metal on a copper current collector.

[0170] Comparative Example 1

[0171] An all-solid-state battery was prepared in the same manner as in Example 1, except that a solid electrolyte layer containing second sulfide-based solid electrolyte particles was prepared and then layered on the positive electrode layer. In this case, the second sulfide-based solid electrolyte particles were not injected into the positive electrode active material layer, resulting in an all-solid-state battery in which the negative electrode layer, solid electrolyte layer, and positive electrode layer were stacked in this order, and the solid electrolyte layer did not wrap around the positive electrode layer but was stacked on it.

[0172] Experimental Example 1: Observation of the interface and interior of the positive electrode of an all-solid-state battery

[0173] In the all-solid-state batteries prepared in Example 1 and Comparative Example 1, the interface of the positive electrode and the interior of the positive electrode were observed.

[0174] The cross sections of the positive electrodes of Example 1 and Comparative Example 1 were observed using a scanning electron microscope (SEM).

[0175] Figure 5 These are scanning electron microscope photographs of cross sections of the positive electrodes of Example 1 and Comparative Example 1.

[0176] Reference Figure 5 , Comparative Example 1 has many macropores compared to Example 1, while relatively no macropores are observed in Example 1. It can also be seen that in Example 1, the small-diameter particle layer at the interface is thicker than that in Comparative Example 1.

[0177] Experimental Example 2: Evaluating the performance of all-solid-state batteries

[0178] Performance evaluation experiments were conducted on the all-solid-state batteries prepared in Example 1 and Comparative Example 1.

[0179] In order to evaluate the performance of the all-solid-state battery, it was charged at a current rate of 0.1C until the voltage reached 4.25V (relative to Li / Li + ), then charged at a current cutoff value of 0.05C while maintaining 4.25V (relative to Li / Li + ). Discharge at a current of 0.1C until it reaches 3V (relative to Li / Li + This process is repeated for one cycle.

[0180] Figure 6 Graphs showing the performance evaluation results of all-solid-state batteries manufactured in Example 1 and Comparative Example 1.

[0181] Reference Figure 6 In Comparative Example 1, the solid electrolyte layer was composed of a layer of small-diameter second solid electrolyte particles, leading to overcharging and short circuiting during external pressurization and charging. In contrast, in Example 1, it can be seen that the second sulfide-based solid electrolyte particles formed in the solid electrolyte layer penetrate into the positive electrode active material layer, forming a dense positive electrode. The small-diameter second sulfide-based solid electrolyte particles, located at a high density near the surface of the positive electrode active material layer, have a shape that stably wraps the positive electrode, enabling stable driving during charge and discharge even under external pressurization.

[0182] Although the present invention has been described above with limited examples and drawings, the present invention is not limited thereto, and a person skilled in the art can make various modifications and changes within the technical idea of ​​the present invention and the equivalent scope of the patent claims set forth below.

[0183] [reference numerals]

[0184] 10: All-solid-state batteries

[0185] 100: Cell

[0186] 110: Positive electrode layer

[0187] 111: positive electrode current collector, 112: positive electrode active material layer

[0188] 120: Solid electrolyte layer

[0189] 130: Negative electrode layer

[0190] 131: negative electrode current collector, 132: negative electrode active material layer

[0191] 200: Stacked cells

[0192] C: crack, D: disintegration

[0193] RF: release film, S: slurry, DB: doctor blade

[0194] P1: First sulfide-based solid electrolyte particle

[0195] P2: Second sulfide-based solid electrolyte particles

Claims

1. An all-solid-state battery comprising a unit cell, in, The unit cell comprises: positive electrode current collector; a positive electrode active material layer, the positive electrode active material layer being in contact with a specific area on one surface of the positive electrode current collector; a solid electrolyte layer surrounding one surface and adjacent side surfaces of the positive electrode active material layer and formed in contact with the positive electrode current collector; and a negative electrode layer, the negative electrode layer being located on the solid electrolyte layer and having an area equal to that of the solid electrolyte layer, The positive electrode active material layer comprises a positive electrode active material, a binder, a conductive material and sulfide-based solid electrolyte particles. The sulfide-based solid electrolyte particles include first sulfide-based solid electrolyte particles and second sulfide-based solid electrolyte particles, and the particle size of the second sulfide-based solid electrolyte particles is smaller than that of the first sulfide-based solid electrolyte particles.

2. The all-solid-state battery according to claim 1, in, The concentration of the second sulfide-based solid electrolyte particles increases from the center toward the surface of the positive electrode active material layer.

3. The all-solid-state battery according to claim 1, in, The positive electrode active material layer has a porosity of 8% to 15%.

4. The all-solid-state battery according to claim 1, in, The area of ​​the solid electrolyte layer is 1.3 to 1.8 times the area of ​​the positive electrode active material layer.

5. The all-solid-state battery according to claim 1, in, The negative electrode layer comprises: a negative electrode current collector; and forming a negative electrode active material layer on the negative electrode current collector, The negative electrode active material layer is stacked to contact the solid electrolyte layer.

6. The all-solid-state battery according to claim 1, in, The negative electrode layer comprises: a negative electrode current collector; and forming an anode-free coating on the negative electrode current collector, The non-anodic coating layer is laminated to contact the solid electrolyte layer.

7. The all-solid-state battery according to claim 1, in, There are two or more battery cells stacked.

8. The all-solid-state battery according to claim 1, in, The all-solid-state battery is of pouch type.

9. A method for manufacturing an all-solid-state battery, comprising a unit cell manufacturing process, wherein the unit cell manufacturing process comprises the following steps: (S1) forming a positive electrode active material layer of a specific area on a positive electrode current collector; (S2) forming a solid electrolyte layer on the positive electrode active material layer so as to surround one surface and adjacent side surfaces of the positive electrode active material layer; (S3) forming a negative electrode layer on the solid electrolyte layer with an area equal to that of the solid electrolyte layer; and (S4) pressurizing and joining the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode layer in a stacking direction, The positive electrode active material layer contained in the unit cell joined after pressurization in step (S4) contains positive electrode active material, binder, conductive material and sulfide-based solid electrolyte particles, and The sulfide-based solid electrolyte particles include first sulfide-based solid electrolyte particles and second sulfide-based solid electrolyte particles, and the particle size of the second sulfide-based solid electrolyte particles is smaller than the particle size of the first sulfide-based solid electrolyte particles.

10. The method for manufacturing an all-solid-state battery according to claim 9, in, The pressure is 300MPa to 700MPa.

11. The method for manufacturing an all-solid-state battery according to claim 9, in, The positive electrode active material layer in step (S1) comprises first sulfide-based solid electrolyte particles, and In the formation process of the solid electrolyte layer in step ( S2 ), when the solid electrolyte layer-forming slurry is applied, a portion of the second sulfide-based solid electrolyte particles contained in the slurry is injected into the positive electrode active material layer.

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