【Technical Field】 [1] This application claims the benefit of priority to Korean Patent Application No. 2020-0066918 filed on June 3, 2020, the disclosure of which is incorporated herein by reference in its entirety. [2] The present invention relates to a pressing apparatus including a fluid and a pressing method using the same, and more particularly to a pressing apparatus including a pressure adjustment portion having a fluid contained therein, whereby pressure applied to target object to be pressed is changed depending on the shape of the target object, and a pressing method using the same. 【Background Art】 [3] With recent development of alternative energies due to air pollution and energy depletion caused as the result of use of fossil fuels, demand for secondary batteries capable of storing electrical energy that is produced has increased. The secondary batteries, which are being capable of being charged and discharged, are 2 intimately used in daily life. For example, the secondary batteries are used in mobile devices, electric vehicles, and hybrid electric vehicles. [4] Secondary batteries used as energy sources of various kinds of electronic devices inevitably used in modern society have been used in a state of being mounted in various kinds of devices, such as mobile devices and electric vehicles. Various shapes of battery cells are required in response to user demand and variety in shape of devices in which secondary batteries are mounted. [5] Various shapes of battery cells may be generally formed by receiving, in a curved or bent case, an electrode having a shape corresponding to the shape of the case or an electrode assembly constituted by stacking electrodes. In order to form various shapes of electrodes, an electrode active material is applied to one surface or opposite surfaces of an electrode current collector formed so as to have a uniform shape, and is then pressed. In addition, for various shapes of electrode assemblies, various shapes of electrodes and separators are stacked, and a lamination process is performed in order to increase the force of coupling therebetween. [6] FIG. 1 is a schematic view of a conventional pressing apparatus. 3 [7] In order to press a target object 10 to be pressed, a pressing portion of the conventional pressing apparatus 20, which is a portion configured to come into contact with the target object 10, is flat. However, the pressing apparatus 20 having the flat pressing portion cannot apply uniform force to a target object 10 having various heights or shapes. [8] That is, stronger force is applied to a portion of the target object 10 that protrudes farther than the other portions of the target object, and weaker force is applied to a portion of the target object 10 that is depressed farther than the other portions of the target object, whereby the target object 10 is not uniformly laminated. In order to solve the above problem, an additional pressing process may be performed with respect to the portion of the target object 10 that is not properly laminated. In this case, however, process time is lengthened and related cost is increased as a result of performing such an additional process. [9] In Patent Document 1, a pattern is formed on the surface of a roll member such that compression force that is transmitted to an electrode and a separator is applied only to some regions thereof. However, there is a problem in that only a portion of a target object is compressed, whereby the entirety of the target object is 4 not uniformly pressed at once. [10] In order to solve the above problem, it is necessary to consider a method capable of uniformly pressing a target object while reducing process time. [11] (Prior Art Document) [12] (Patent Document 1) Korean Patent Application Publication No. 2017-0099213 (2017.08.31) 【Disclosure】 【Technical Problem】 [13] The present invention has been made in view of the above problems, and it is an object of the present invention to provide a pressing apparatus capable of applying uniform pressing force to a target object to be pressed. [14] It is another object of the present invention to easily produce various shapes of electrodes or electrode assemblies using the pressing apparatus. It is a further object of the present invention to simplify an electrode and electrode assembly manufacturing process and to reduce a defect rate, whereby it is possible to reduce production cost. 【Technical Solution】 [15] In order to accomplish the above objects, a 5 pressing apparatus according to the present invention may include a contact portion having a shape or position configured to be changed depending on the shape of a target object to be pressed, a pressing portion configured to apply uniform force to the contact portion, and a pressure adjustment portion located between the contact portion and the pressing portion, the pressure adjustment portion having a fluid contained therein. [16] In addition, the contact portion may have a pattern configured to change a pressure applied to the target object depending on the shape of the target object. [17] The pattern may be an oblique pattern, an Xshaped pattern, or a dot type pattern having a plurality of micro-scale protrusions. [18] The contact portion may have a plurality of protrusions configured to be individually movable. [19] The pressure adjustment portion may be individually connected to the contact portion. [20] In addition, the pressing portion may be individually or integrally connected to the pressure adjustment portion. [21] The fluid of the pressure adjustment portion may be connected to the plurality of protrusions. [22] In addition, the fluid of the pressure adjustment 6 portion may occupy less than 90% of the pressure adjustment portion. [23] In addition, the pressing apparatus may include an upper roll including the contact portion, the pressing portion, and the pressure adjustment portion and a lower roll having the same identical construction as the upper roll. [24] The present invention provides an electrode and electrode assembly manufacturing method including (S1) preparing an electrode or an electrode assembly that is the target object to be pressed, (S2) disposing the target object in the pressing apparatus, and (S3) pressing the target object using the pressing apparatus. [25] In step (S3), the pressing apparatus may be deformed depending on the shape of the target object or a pressing force applied to the contact portion, configured to come into contact with the target object, may be changed depending on the shape of the target object. [26] The present invention provides a unit cell including the above-mentioned electrode or electrode assembly. In addition, the present invention provides a battery module or a battery pack including the unit cell. In addition, the present invention provides a device having the unit cell, the battery module, or the battery 7 pack mounted therein. [27] In the present invention, one or more constructions that do not conflict with each other may be selected and combined from among the above constructions. 【Advantageous Effects】 [28] As is apparent from the above description, a pressing apparatus according to the present invention includes a contact portion having a shape changeable depending on the shape of a target object to be pressed, a pressing portion configured to apply uniform force to the contact portion, and a pressure adjustment portion configured to adjust the force applied from the pressing portion differently depending on the shape of the target object in order to change the shape of the contact portion, whereby it is possible to apply uniform pressing force to the target object irrespective of the shape of the target object. [29] In addition, the target object, to which uniform pressing force is applied irrespective of the shape of the target object, may be uniformly laminated while the uniform shape of the target object is maintained. As a result, all parts of the target object are uniformly laminated, whereby it is possible to obtain a target 8 object, the uniform shape of which is maintained. Furthermore, defects of the target object at a specific part thereof are remarkably reduced. [30] In addition, it is not necessary to perform an additional process for uniform lamination, whereby it is possible to reduce time and cost incurred in the process, which is economical. [31] 【Description of Drawings】 [32] FIG. 1 is a schematic view of a conventional pressing apparatus. [33] FIG. 2 is a schematic view of a pressing apparatus according to the present invention. [34] FIG. 3 is a schematic view of the pressing apparatus according to the present invention configured to have a pressing roll type structure. [35] FIG. 4 is a schematic view showing the interior of a pressing apparatus according to a first embodiment of the present invention. [36] FIG. 5 is a schematic view showing the interior of a pressing apparatus according to a second embodiment of the present invention. [37] FIG. 6 is a photograph showing the shape of a pattern of a contact portion according to the present 9 invention. 【Best Mode】 [38] Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings such that the preferred embodiments of the present invention can be easily implemented by a person having ordinary skill in the art to which the present invention pertains. In describing the principle of operation of the preferred embodiments of the present invention in detail, however, a detailed description of known functions and configurations incorporated herein will be omitted when the same may obscure the subject matter of the present invention. [39] In addition, the same reference numbers will be used throughout the drawings to refer to parts that perform similar functions or operations. In the case in which one part is said to be connected to another part in the entire specification, not only may the one part be directly connected to the other part, but also, the one part may be indirectly connected to the other part via a further part. In addition, that a certain element is included does not mean that other elements are excluded, but means that such elements may be further included unless mentioned otherwise. 10 [40] FIG. 2 is a schematic view of a pressing apparatus according to the present invention, FIG. 3 is a schematic view of the pressing apparatus according to the present invention configured to have a pressing roll type structure, FIG. 4 is a schematic view showing the interior of a pressing apparatus according to a first embodiment of the present invention, and FIG. 5 is a schematic view showing the interior of a pressing apparatus according to a second embodiment of the present invention. [41] The pressing apparatus 200 according to the present invention is characterized in that uniform pressure is applied to a target object 100 irrespective of the shape of the target object 100. [42] The target object 100 may be an electrode having an active material applied to one surface or opposite surfaces of an electrode current collector or an electrode assembly including electrodes, each of which is formed as described above, i.e. a positive electrode and a negative electrode, which are stacked in the state in which a separator is interposed therebetween. [43] The positive electrode includes a positive electrode active material layer applied to at least one surface of a positive electrode current collector. The positive electrode active material layer may be 11 manufactured by applying a positive electrode mixture of a positive electrode active material, a conductive agent, and a binder. A filler may be further added to the positive electrode mixture as needed. [44] In general, the positive electrode current collector is manufactured so as to have a thickness of 3 μm to 500 μm. The positive electrode current collector is not particularly restricted as long as the positive electrode current collector exhibits high conductivity while the positive electrode current collector does not induce any chemical change in a battery to which the positive electrode current collector is applied. For example, the positive electrode current collector may be made of stainless steel, aluminum, nickel, or titanium. Alternatively, the positive electrode current collector may be made of aluminum or stainless steel, the surface of which is treated with carbon, nickel, titanium, or silver. Specifically, aluminum may be used. The positive electrode current collector may have a microscale uneven pattern formed on the surface thereof so as to increase the force of adhesion to the positive electrode active material layer. The positive electrode current collector may be configured in any of various forms, such as a film, a sheet, a foil, a net, a porous body, a foam body, or a non-woven fabric body. 12 [45] In addition to the positive electrode active material particles, the positive electrode active material may be constituted, for example, by a layered compound, such as a lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium manganese oxide represented by the chemical formula Li1+xMn2-xO4 (where x = 0 to 0.33) or a lithium manganese oxide, such as LiMnO3, LiMn2O3, or LiMnO2; a lithium copper oxide (Li2CuO2); a vanadium oxide, such as LiV3O8, LiV3O4, V2O5, or Cu2V2O7; an Ni-sited lithium nickel oxide represented by the chemical formula LiNi1-xMxO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); a lithium manganese composite oxide represented by the chemical formula LiMn2-xMxO2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and x = 0.01 to 0.1) or the chemical formula Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced by alkaline earth metal ions; a disulfide compound; or Fe2(MoO4)3. However, the present invention is not limited thereto. [46] The conductive agent is generally added so that the conductive agent accounts for 0.1 weight% to 30 weight% based on the total weight of the mixture including the positive electrode active material. The conductive agent is not particularly restricted as long 13 as the conductive agent exhibits high conductivity without inducing any chemical change in a battery to which the conductive agent is applied. For example, graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fiber, such as carbon fiber or metallic fiber; carbon fluoride powder; metallic powder, such as aluminum powder, or nickel powder; conductive whisker, such as a zinc oxide or potassium titanate; a conductive metal oxide, such as a titanium oxide; or a conductive material, such as a polyphenylene derivative, may be used as the conductive agent. [47] The binder, which is included in the positive electrode, is a component assisting in binding between the active material and the conductive agent and in binding with the current collector. The binder is generally added in an amount of 0.1 weight% to 30 weight% based on the total weight of the mixture including the positive electrode active material. As examples of the binder, there may be used polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer, 14 sulfonated ethylene-propylene-diene monomer, styrene butadiene rubber, fluoro rubber, and various copolymers. [48] The negative electrode is manufactured by applying a negative electrode active material to one surface or opposite surfaces of a negative electrode current collector and drying the same, whereby a negative electrode active material layer is provided at one surface of the negative electrode. The above-described components may be selectively further included as needed. [49] Since the negative electrode is provided as a single-sided negative electrode having a negative electrode active material layer provided only at one surface of a negative electrode current collector, the space of a pouch-shaped secondary battery occupied by the negative electrode is reduced, whereby the capacity of the pouch-shaped secondary battery is increased. [50] As the negative electrode active material, for example, there may be used carbon, such as a nongraphitizing carbon or a graphite-based carbon; a metal composite oxide, such as LixFe2O3 (0≤x≤1), LixWO2 (0≤x≤1), or SnxMe1-xMe’yOz (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, 2 and 3 elements of the periodic table, halogen; 0