Title of invention: All-solid-state battery using lithium metal as negative electrode Technical field [One] This application claims priority based on Korean Patent Application No. 10-2018-0098857 filed on August 23, 2018. The present invention relates to an electrode assembly for an all-solid-state battery comprising a solid electrolyte as an electrolyte material. In particular, the all-solid-state battery uses lithium metal as a negative electrode. [2] Background [3] Secondary batteries have been mainly applied to small-sized fields such as mobile devices and notebook computers, but in recent years, their application direction has been expanded to mid- to large-sized fields, mainly energy storage systems (ESS) or electric vehicles (EV). It is expanding to fields that require high energy and high output in relation to such as. In the case of such a medium-sized secondary battery, unlike small-sized batteries, the operating environment such as temperature and impact is severe, and since more batteries must be used, it is necessary to ensure safety along with excellent performance or an appropriate price. Since most of the secondary batteries currently commercialized use an organic liquid electrolyte in which a lithium salt is dissolved in an organic solvent, there is a potential risk of ignition and explosion, including leakage. [4] Therefore, in recent years, all-solid-state batteries are being developed.All-solid-state batteries are batteries using non-flammable inorganic solid electrolytes and are thermally more thermally compared to lithium secondary batteries using conventional flammable organic liquid electrolytes. It has the advantage of high stability. An all-solid-state battery generally has a laminated structure of a negative electrode current collector layer, a negative electrode layer, a solid electrolyte layer, a positive electrode layer and a positive electrode current collector layer. Among the prior art for such an all-solid-state battery, processes suitable for mass production include'Korean Intellectual Property Office Registration Patent No. 10-1506833 slurry, a method of manufacturing a solid electrolyte layer, a method of manufacturing an electrode active material layer, and a method of manufacturing an all-solid-state battery'. The same slurry application technique is being developed. [5] On the other hand, when an all-solid battery using lithium metal as a negative active material is used as a high-capacity battery, the volume of the negative electrode changes very severely as lithium is stripping/plating. In order to reduce the interface resistance between the negative electrode and the solid electrolyte layer (polymer electrolyte), the polymer electrolyte, which is a material for the solid electrolyte layer, is generally required to have high viscosity. And, in order to increase the energy density, the thickness of the solid electrolyte layer should be as thin as possible. Therefore, the solid electrolyte layer is generally very sticky due to high viscosity at the interface, and its mechanical strength is weak due to its thin thickness. In order to perfectly align the electrodes when manufacturing the electrode assembly, the area of ​​the cathode is generally designed to be larger than the area of ​​the anode, and the area of ​​the solid electrolyte layer is larger than the area of ​​the cathode. At this time, in the lithium metal used as the negative electrode, lithium is stripping/plating on the surface facing the positive electrode, and lithium (Li) does not approach the rest (parts not facing the positive electrode). Therefore, considering the charging situation, as plating occurs in the lithium (Li) metal layer, lithium (Li) is plated in the portion facing the positive electrode, and the thickness of the lithium metal becomes thick. At this time, the solid electrolyte layer may be damaged as a step occurs between a portion facing the anode and a portion that is not. 1 is a schematic diagram showing a cross section of an electrode assembly for an all-solid-state battery of a conventional conventional shape, wherein the electrode assembly includes a positive electrode 10, a negative electrode 40, and a solid electrolyte 20 interposed between the positive electrode and the negative electrode. Includes. As the charging and discharging of the all-solid-state battery is repeated, lithium plating 50 is generated in the lithium metal layer, which is the negative electrode, and the thickness of the lithium metal increases in the portion of the negative electrode that faces the positive electrode, and a step is generated in the negative electrode layer. FIG. 2 schematically shows the formation of a step in the negative electrode layer during charging in a typical all-solid-state battery. Furthermore, when manufacturing the electrode assembly, there is a high possibility that the polymer-based solid electrolyte layer is damaged at the edge of the solid electrolyte layer, resulting in a short circuit between the positive electrode and the negative electrode. [6] Detailed description of the invention Technical challenge [7] An object of the present invention is to provide an electrode assembly for an all-solid battery with improved safety. In particular, the present invention is designed to prevent damage to the solid electrolyte layer due to the occurrence of a step even if a step occurs in the negative electrode layer due to a change in the thickness of the negative electrode layer, such as an increase or decrease in the thickness of a part of the negative electrode layer according to charging and discharging in the electrode assembly for an all-solid-state battery. An object of the present invention is to provide an electrode assembly having a new structure. In addition, it will be readily appreciated that other objects and advantages of the present invention can be realized by means or methods described in the claims and combinations thereof. [8] Means of solving the task [9] The present invention relates to an all-solid-state battery. A first aspect of the present invention relates to such an all-solid battery, wherein the electrode assembly includes a negative electrode, a positive electrode, and an electrode assembly in which a solid electrolyte layer is interposed between the positive electrode and the negative electrode, and the negative electrode is The negative electrode active material contains lithium metal, and the solid electrolyte layer, the negative electrode and the positive electrode are all the same, or the area decreases in the order of the solid electrolyte layer, the negative electrode and the positive electrode based on the area of ​​the laminated surface, and the negative electrode is interviewed with the solid electrolyte layer. However, it is disposed on the inside of the surface of the solid electrolyte layer, the positive electrode is indirectly in contact with the negative electrode through the solid electrolyte layer, but is disposed on the inside of the negative electrode, and a protective layer containing a polymer resin between the negative electrode and the solid electrolyte layer The protective layer is further provided, and the protective layer is in the form of a frame having an edge portion having a predetermined width and an opening surrounded by the edge portion, and the area of ​​the opening is narrower than that of the anode, and the protective layer is provided so that the opening is located inside the anode surface. It is placed. [10] In a second aspect of the present invention, in the first aspect, the solid electrolyte layer includes a polymer-based solid electrolyte. [11] The third aspect of the present invention is according to any one of the above-described aspects, wherein the polymer-based solid electrolyte is a polyether-based polymer, a polycarbonate-based polymer, an acrylate-based polymer, a polysiloxane-based polymer, a phosphazene-based polymer, a polyethylene derivative, an alkyl It includes at least one selected from among the ren oxide derivatives. [12] A fourth aspect of the present invention is that in any one of the above-described aspects, the outer peripheral portion of the negative electrode does not directly contact the solid electrolyte layer by the edge portion. [13] A fifth aspect of the present invention is that the protective layer has a thickness of 1/10 to 1/2 of the thickness of the solid electrolyte layer in any one of the above-described aspects. [14] In a sixth aspect of the present invention, in any one of the above-described aspects, the protective layer edge portion protrudes outside the solid electrolyte layer by a predetermined width. [15] A seventh aspect of the present invention is that in any one of the above-described aspects, the anode is stacked so that the periphery of the anode is positioned inside the edge portion of the protective layer. [16] In an eighth aspect of the present invention, in any one of the aforementioned aspects, the solid electrolyte layer, the negative electrode, and the positive electrode all have the same area based on the area of ​​the laminated surface, and the protective layer has an outer part having a predetermined width among the rims. It protrudes out of the solid electrolyte layer, and the protruding portion is bent in the direction of the solid electrolyte layer to surround the laminated cross section of the solid electrolyte layer and the positive electrode. [17] In a ninth aspect of the present invention, in the eighth aspect, the protective layer is bent in such a manner that the end of the protruding portion covers all or part of the outer periphery of the anode surface. [18] A tenth aspect of the present invention is to include at least one of polyethylene and polypropylene in any one of the above-described aspects, the protective layer. [19] Effects of the Invention [20] In the present invention, the protective layer of the polyolefin material has higher mechanical strength, lower flexibility, and lower viscosity than the solid electrolyte layer. Accordingly, the electrode assembly according to the present invention is provided with a protective layer in the form of a frame, so that lithium plating is generated on the anode and the facing portion (inner portion of the cathode surface) of the cathode layer surface, and the outer peripheral portion of the cathode surface and the inner surface surrounded by the outer peripheral portion Even if a step occurs in the protective layer, the protective layer moves upward along the step, and as the protective layer moves, the outer portion of the electrolyte membrane is supported by the protective layer and moves upward together, so that damage to the solid electrolyte layer due to plating and step formation is prevented. . [21] Brief description of the drawing [22] The drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to better understand the technical idea of ​​the present invention together with the content of the present invention, so the present invention is limited to the matters described in such drawings. Is not interpreted. Meanwhile, the shape, size, scale, or ratio of elements in the drawings included in the present specification may be exaggerated to emphasize a clearer description. [23] 1 is a cross-sectional view of an electrode assembly for an all-solid-state battery according to the prior art. [24] 2 is a cross-sectional view of an electrode assembly for an all-solid-state battery according to the prior art, schematically showing that lithium plating occurs on the surface of the negative electrode due to repeated charging and discharging of the battery, resulting in a thicker thickness of the negative electrode. . [25] 3A is a schematic diagram showing a cross section of an electrode assembly for an all-solid-state battery according to an embodiment of the present invention. [26] 3B shows the width of each component. [27] 4 is a cross-sectional view of an electrode assembly for an all-solid-state battery according to an embodiment of the present invention, schematically illustrating that lithium plating occurs on the surface of the negative electrode due to repeated charging and discharging of the battery, resulting in a thicker thickness of the negative electrode. Is shown. [28] 5 is an exploded perspective view of an electrode assembly for an all-solid-state battery according to an embodiment of the present invention. [29] 6 is a view showing an electrode assembly for an all-solid-state battery according to an embodiment of the present invention, in which a portion of the outer edge of the protective layer having a predetermined width protrudes out of the solid electrolyte layer to surround the laminated cross section of the solid electrolyte layer and the positive electrode. Is shown. Mode for carrying out the invention [30] Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to their usual or dictionary meanings, and the inventor appropriately defines the concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of ​​the present invention based on the principle that it can be done. Accordingly, the embodiments described in the present specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and do not represent all the technical ideas of the present invention, so that they can be replaced at the time of application. It should be understood that there may be various equivalents and variations. [31] [32] In the entire specification of the present application, when a certain part "includes" a certain constituent element, it means that other constituent elements may be further included rather than excluding other constituent elements unless otherwise stated. [33] [34] In addition, the terms "about" and "substantially" used throughout the specification of the present application are used as a meaning at or close to the numerical value when a manufacturing and material tolerance specific to the stated meaning is presented to aid understanding of the present application. In order to prevent unreasonable use by unscrupulous infringers of the stated disclosures, exact or absolute figures are used. [35] [36] In the entire specification of the present application, the description of "A and/or B" means "A or B or both". [37] [38] Certain terms used in the detailed description of the invention that follow are for convenience and are not limiting. Words such as "inside", "outside", "right", "left", "top surface" and "bottom" indicate directions in the drawings to which reference is made. The words'inwardly' and'outwardly' refer to a direction towards or away from the geometric center of the specified device, system and members, respectively. “Forward”, “rear”, “upward”, “downward” and related words and phrases represent positions and orientations in the drawings to which reference is made and should not be limited. These terms include the words listed above, their derivatives, and words of similar meaning. [39] [40] The present invention relates to an electrode assembly for an electrochemical device. In the present invention, the electrochemical device is a device that converts chemical energy into electrical energy through an electrochemical reaction, and is a concept including a primary battery and a secondary battery, and the secondary battery is capable of charging and discharging. , Lithium ion battery, nickel-cadmium battery, nickel-hydrogen battery, etc. In one embodiment of the present invention, the electrochemical device may be a lithium ion battery, preferably an all-solid battery using a solid electrolyte as an electrolyte. In addition, in the present invention, the all-solid-state battery is preferably a lithium metal battery using lithium metal as a negative electrode. [41] [42] The electrode assembly of the present invention will be described in more detail with reference to the accompanying drawings in the present specification. 3A and 3B schematically show a cross-section of an electrode assembly for an all-solid-state battery according to an embodiment of the present invention. In one embodiment of the present invention, the electrode assembly includes a positive electrode 10, a negative electrode 40, and a solid electrolyte layer 20 interposed between the positive electrode and the negative electrode, and a predetermined width between the negative electrode and the solid electrolyte layer A protective layer 30 is interposed. [43] [44] In the electrode assembly, the area of ​​the solid electrolyte layer, the negative electrode, and the positive electrode decreases in order based on the area of ​​the laminated surface. The negative electrode faces the solid electrolyte layer but is disposed inside the surface of the solid electrolyte layer so that it does not protrude outside the solid electrolyte layer. In addition, the positive electrode indirectly contacts the negative electrode through the solid electrolyte layer, but is disposed inside the surface of the negative electrode. 3A and 3B are cross-sectional views of an electrode assembly according to an embodiment of the present invention, in which both ends of the anode surface are disposed to be included within the width of the cathode surface, and both ends of the cathode surface are the width of the solid electrolyte layer It is arranged to be included within. [45] [46] In one embodiment of the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer including a positive electrode active material and a solid electrolyte on at least one surface of the current collector. The positive electrode active material layer may further include a conductive material and a binder resin, if necessary. The positive electrode active material is not limited thereto, but a layered compound such as lithium manganese composite oxide (LiMn 2 O 4 , LiMnO 2, etc.), lithium cobalt oxide (LiCoO 2 ), and lithium nickel oxide (LiNiO 2 ), or 1 or its Compounds substituted with the above transition metals; Lithium manganese oxides such as the formula Li 1 + x Mn 2 - x O 4 (wherein x is 0 to 0.33), LiMnO 3 , LiMn 2 O 3 , and LiMnO 2 ; Lithium copper oxide (Li 2CuO 2 ); Vanadium oxides such as LiV 3 O 8 , LiV 3 O 4 , V 2 O 5 , and Cu 2 V 2 O 7 ; Lithium nickel oxide represented by the formula LiNi 1 - x M x O 2 (here, M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn 2 - x M x O 2 (where M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 ~ 0.1), Li a Mn x Ni y Co z O 2 (0.5