Electrode assembly and secondary battery including same

Abstract

The present invention discloses an electrode assembly and a secondary battery including the same, in which a part or the whole of the laminated structure is pyramidal, and which reduces a short circuit phenomenon that occurs at the side portion during battery operation. The electrode assembly is an electrode assembly in which a negative electrode layer having a negative electrode active material layer on both sides of a negative electrode current collector and a positive electrode layer having a first positive electrode active material layer and a second positive electrode active material layer on both sides of a positive electrode current collector are alternately laminated with a solid electrolyte layer interposed therebetween, the first positive electrode active material layer and the second positive electrode active material layer in the positive electrode layer extending toward both ends of the positive electrode current collector based on the center line of the positive electrode current collector have different lengths, and among them, the length of the negative electrode active material layer facing the first positive electrode active material layer, which is relatively short, is equal to or shorter than the length of the second positive electrode active material layer, which is relatively long.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0130634 dated October 12, 2022, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly and a secondary battery including the same, and more particularly to an electrode assembly in which a part or the entire laminated structure has a pyramid shape, and which reduces a short circuit phenomenon that occurs at a side portion during battery operation, and a secondary battery including the same. [Background technology]

[0003] As technological development and demand for mobile devices and automobiles has explosively increased, more and more research has been conducted on secondary batteries having high energy density, discharge voltage, and excellent output stability. Examples of such secondary batteries include lithium-based secondary batteries such as lithium-sulfur batteries, lithium-ion batteries, and lithium-ion polymer batteries. In addition, such secondary batteries can be classified into cylindrical, rectangular, pouch, and other types depending on their shapes, and among them, interest in and demand for pouch-type battery cells is gradually increasing. Pouch-type battery cells can be stacked with a high degree of integration, have a high energy density per weight, are inexpensive, and are easily deformable. Therefore, pouch-type battery cells can be manufactured in shapes and sizes applicable to various mobile devices and automobiles.

[0004] Such a pouch-type battery cell generally has a structure in which a large number of unit cells, each including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, are stacked (i.e., an electrode assembly or stack cell). After the electrode assembly is housed in a battery case, an electrolyte solution is injected or a solid electrolyte is provided in the electrode assembly from the beginning to produce a product (i.e., an all-solid-state battery).

[0005] Among these, all-solid-state batteries are superior in terms of safety compared to other types of secondary batteries, and are attracting attention especially in the fields of electric vehicles and mobile devices. In other words, all-solid-state batteries are batteries in which the electrolyte used in normal lithium secondary batteries is replaced from liquid to solid, which significantly improves safety by eliminating the use of flammable solvents and completely eliminating the risk of fire or explosion caused by the decomposition reaction of conventional electrolytes. In addition, all-solid-state batteries have the advantage of being able to dramatically improve the energy density relative to the mass and volume of the battery, since Li metal or Li alloy can be used as the anode material.

[0006] In the manufacturing process of such all-solid-state batteries, a warm isostatic pressing (WIP) process is generally applied to bond the interface between the electrodes and the solid electrolyte. FIG. 1 is a schematic side cross-sectional view showing the electrode lamination form of a conventional all-solid-state battery, and FIG. 2 is a schematic view showing one side cross-section of a conventional all-solid-state battery in an isostatically pressed state. That is, as shown in FIG. 1, a conventional all-solid-state battery generally has a form in which a positive electrode (20, where 20a is a positive electrode current collector) having a length shorter than that of the negative electrode (10) is interposed between negative electrodes (10, where 10a is a negative electrode current collector) (at this time, the solid electrolyte layers respectively positioned between the positive and negative electrodes are not shown in order to more clearly show the positional relationship between the electrodes). However, when isostatic pressing (WIP) is performed to bond the interface between the electrode and solid electrolyte (30: metal plate used for isostatic pressing), as shown in Figure 2, the end (or side) of the anode (10) located at the top is bent, and during this process, cracks are likely to occur in the solid electrolyte layer and the anode layer. Since appropriate pressure cannot be applied to this part during operation, this creates conditions that are prone to lithium dendrite growth, resulting in a short circuit.

[0007] In other words, because conventional solid-state batteries have a shape as shown in Figure 1 or 2, a short circuit occurs between the end of the upper anode and the side of the opposite end of the cathode during operation. Therefore, it is necessary to find a method that has an electrode shape that can alleviate bending of the anode after isostatic pressing and can alleviate and suppress the short circuit between the cathode and anode during battery operation. Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE PRESENTLY PREFERRED EMBODIMENTS An object of the present invention is to provide an electrode assembly and a secondary battery including the same, in which a part or the entire laminated structure has a pyramidal shape, thereby mitigating a short circuit phenomenon that occurs at the side during battery operation. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides an electrode assembly in which an anode layer having an anode active material layer on both sides of an anode current collector and a cathode layer having a first cathode active material layer and a second cathode active material layer on both sides of a cathode current collector are alternately stacked with a solid electrolyte layer interposed therebetween, wherein the first and second cathode active material layers in the cathode layer, which extend toward both ends of the cathode current collector based on a center line of the cathode current collector, have different lengths, and the length of the anode active material layer facing the first cathode active material layer, which is relatively short, is equal to or shorter than the length of the second cathode active material layer, which is relatively long.

[0010] The present invention also provides a secondary battery including the electrode assembly; and a housing case that houses the electrode assembly. Effect of the Invention

[0011] According to the electrode assembly and the secondary battery including the same according to the present invention, a part or the entire laminated structure has a pyramidal shape, which is advantageous in that a short circuit phenomenon occurring at the side portion during operation of the battery is mitigated. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic side cross-sectional view showing an electrode lamination configuration of a typical all-solid-state battery. [Diagram 2] FIG. 1 is a schematic diagram showing a half-section of a typical all-solid-state battery in a state where it is isostatically pressed. [Diagram 3] FIG. 2 is a schematic side cross-sectional view showing an electrode lamination form of an all-solid-state battery according to an embodiment of the present invention. [Figure 4] FIG. 2 is a schematic diagram showing a half-section of an all-solid-state battery according to an embodiment of the present invention in a state where the battery is subjected to isostatic pressure. [Diagram 5] FIG. 2 is a schematic side cross-sectional view showing an electrode lamination form of an all-solid-state battery according to another embodiment of the present invention. [Figure 6] 4 is a graph comparing life characteristics and capacity of secondary batteries manufactured according to an embodiment of the present invention and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will now be described in detail with reference to the accompanying drawings.

[0014] FIG. 3 is a schematic side cross-sectional view showing an electrode lamination form of an all-solid-state battery according to an embodiment of the present invention, and FIG. 4 is a schematic view showing one side cross-section of the all-solid-state battery according to an embodiment of the present invention in a state in which it is isostatically pressed.

[0015] As shown in FIG. 3, the electrode assembly according to the present invention is formed by alternately laminating an anode layer (100) having an anode active material layer (100b) on both sides of an anode current collector (100a); and a cathode layer (200) having a first cathode active material layer (200b) and a second cathode active material layer (200c) on both sides of a cathode current collector (200a), with a solid electrolyte layer (solid electrolyte layer 100) between the anode layer (100) and the cathode layer (200) interposed therebetween. In the electrode assembly having a positive electrode layer (200) having a first positive electrode active material layer (200b) and a second positive electrode active material layer (200c) extending toward both ends of the positive electrode current collector (200a) based on the center line of the positive electrode current collector (200a) have different lengths, and the length of the negative electrode active material layer facing the first positive electrode active material layer (200b), which has a relatively short length, is equal to or shorter than the length of the second positive electrode active material layer (200c), which has a relatively long length.

[0016] All-solid-state batteries are superior to other types of secondary batteries in terms of safety, and are attracting attention especially in the fields of electric vehicles and mobile devices. In other words, all-solid-state batteries are batteries in which the electrolyte used in normal lithium secondary batteries is replaced from liquid to solid, which significantly improves safety by eliminating the use of flammable solvents and completely eliminating the risk of fire or explosion caused by the decomposition reaction of conventional electrolytes. In addition, all-solid-state batteries have the advantage of being able to dramatically improve the energy density relative to the mass and volume of the battery, since Li metal or Li alloy can be used as the anode material.

[0017] In the manufacturing process of such solid-state batteries, a warm isostatic pressing (WIP) process is generally applied to bond the interface between the electrodes and the solid electrolyte. That is, a typical solid-state battery generally has a structure in which a positive electrode (20, where 20a is a positive electrode current collector) having a length shorter than that of the negative electrode (10) is interposed between the negative electrodes (10, where 10a is a negative electrode current collector) as shown in FIG. 1 (at this time, the solid electrolyte layers respectively positioned between the positive and negative electrodes are not shown in order to more clearly show the positional relationship between the electrodes). This is to prevent the problem of lithium (Li) being precipitated at the sliding portion due to the difference in contact area between the positive and negative electrodes caused by the electrode sliding phenomenon, and this lithium precipitation problem can cause a decrease in the life of the battery and even cause explosions and fires.

[0018] Nevertheless, when isostatic pressing (WIP) is performed to bond the interface between the electrode and solid electrolyte (30: metal plate used in isostatic pressing), the end (or side) of the upper anode (10) is bent as shown in Fig. 2, and cracks are likely to occur in the solid electrolyte layer and anode layer during this process, and since appropriate pressure cannot be applied to this part during operation, it becomes a condition in which lithium dendrites are likely to grow, resulting in a short circuit. In other words, since conventional all-solid-state batteries have the form shown in Fig. 1 or Fig. 2, a short circuit occurs between the end of the upper anode and the end side of the cathode facing it during operation.

[0019] However, the applicant has configured the lengths of the positive electrode active material layers (200b, 200c) located on both sides of the positive electrode current collector (200a) to be different from each other, and configured the length of the negative electrode layer (upper negative electrode layer (100) with reference to FIG. 3) facing the relatively short positive electrode active material layer (200b) to be the same as or shorter than the relatively long positive electrode active material layer (200c). The present invention has such an electrode configuration, which has the advantage of mitigating bending of the negative electrode after isostatic pressing (i.e., creating conditions that make it difficult for lithium dendrite growth to occur) and suppressing the short circuit phenomenon between the positive electrode and the negative electrode that occurs during battery operation.

[0020] More specifically, all the positive electrode layers (200) included in the electrode assembly according to the present invention each include a first positive electrode active material layer (200b) and a second positive electrode active material layer (200c) on both sides of the positive electrode current collector (200a). The lengths of the positive electrode active material layers (200b, 200c) located on both sides of the positive electrode current collector (200a) must be different from each other. For example, referring to FIG. 3, in one positive electrode layer (200), a positive electrode active material layer having a relatively short length corresponds to the first positive electrode active material layer (200b), and a positive electrode active material layer having a relatively long length corresponds to the second positive electrode active material layer (200c). Therefore, the degree of bending of the negative electrode active material layer after isostatic pressing is reduced. Furthermore, as shown in FIGS. 3 and 4, the length of the negative electrode active material layer facing the relatively short positive electrode active material layer is the same as or shorter than the length of the relatively long positive electrode active material layer, and therefore the negative electrode active material layer facing the first positive electrode active material layer (200b) does not come into contact with the second positive electrode active material layer (200c) that is longer than the first positive electrode active material layer (200b) after being isostatically pressed.

[0021] At this time, the length ratio of the second positive electrode active material layer (200c) to the first positive electrode active material layer (200b) may be 1:0.3 to 0.9, preferably 1:0.3 to 0.7, and more preferably 1:0.5 to 0.6. If the length ratio of the second positive electrode active material layer (200c) to the first positive electrode active material layer (200b) is out of the above range, the first positive electrode active material layer (200b) may not be able to perform its original function, or the length difference between the first positive electrode active material layer (200b) and the negative electrode layer facing it may become too small, causing a problem of lithium (Li) being precipitated at the electrode sliding portion.

[0022] The positive electrode layer (200) is configured to adjust the length of the negative electrode layer (100) facing it to a level where short circuit does not occur or is minimized. That is, in one positive electrode layer (200), the length of the negative electrode active material layer facing the relatively short positive electrode active material layer (i.e., the first positive electrode active material layer, 200b) must be equal to or shorter than the length of the relatively long positive electrode active material layer (i.e., the second positive electrode active material layer, 200c). If the length of the negative electrode active material layer facing the first positive electrode active material layer (200b) is longer than the length of the second positive electrode active material layer (200c), the negative electrode active material layer is likely to bend toward the side of the second positive electrode active material layer (200c) and cause a short circuit during operation.

[0023] In addition, in the present invention, the length of the negative electrode active material layer facing the first positive electrode active material layer (200b) is limited to be equal to or shorter than the length of the second positive electrode active material layer (200c), but this is for preventing short circuiting between the positive and negative electrodes as much as possible, as described above. Therefore, even if the length of the negative electrode active material layer facing the first positive electrode active material layer (200b) is longer than the length of the second positive electrode active material layer (200c) to a level that does not cause a short circuiting phenomenon, it can be said to be within the scope of the present invention.

[0024] Meanwhile, as described above, the length of the negative electrode active material layer facing the first positive electrode active material layer (200b) may be shorter than the length of the second positive electrode active material layer (200c), but must be equal to or longer than the length of the first positive electrode active material layer (200b). However, it is preferable that the length of the negative electrode active material layer facing the first positive electrode active material layer (200b) is longer than the length of the first positive electrode active material layer (200b). Otherwise, as described above, there is a risk of lithium (Li) being precipitated at the electrode sliding portion.

[0025] The length of the negative electrode active material layer facing the second positive electrode active material layer (200c) must be equal to or greater than the length of the second positive electrode active material layer (200c). However, it is preferable that the length of the negative electrode active material layer facing the second positive electrode active material layer (200c) is greater than the length of the second positive electrode active material layer (200c). Otherwise, as described above, a problem of lithium (Li) deposition on the electrode sliding portion may occur. In addition, it is preferable that the length of the negative electrode active material layer facing the second positive electrode active material layer (200c) is greater than the length of the negative electrode active material layer facing the first positive electrode active material layer (200b). In addition, the negative electrode active material layers provided on both sides of the negative electrode current collector may have different lengths, but are preferably the same. In addition, the length of the positive electrode current collector (200a) must be longer than the length of the first positive electrode active material layer (200b) and equal to or longer than the length of the second positive electrode active material layer (200c) so that the negative electrode active material layer facing the first positive electrode active material layer (200b) does not come into contact with the second positive electrode active material layer (200c) even after isostatic pressing.

[0026] When the electrode assembly has the above electrode configuration, even if isostatic pressing (WIP) is performed for electrode-solid electrolyte interface bonding, the positive and negative electrodes do not come into contact with each other, for example, the end (or side) of the upper negative electrode and the end of the lower negative electrode are spaced apart by a considerable distance, as shown in Fig. 4, so the possibility of a short circuit occurring between the positive and negative electrodes during battery operation can be eliminated or minimized (300 in Fig. 4: metal plate used during isostatic pressing). This is a unique feature of the present invention in contrast to the conventional case (corresponding to Fig. 2) in which the end of the negative electrode is bent during isostatic pressing for electrode-solid electrolyte interface bonding, and a short circuit between the positive and negative electrodes inevitably occurs during battery operation.

[0027] Meanwhile, in the above, the description has been given based on the pyramidal electrode assembly (i.e., an electrode assembly in which the entire stacking structure is pyramidal) as shown in FIG. 3 and FIG. 4, but the present invention is not limited thereto (i.e., a part or the entire stacking structure of the electrode assembly is pyramidal). FIG. 5 is a schematic side cross-sectional view showing an electrode stacking form of an all-solid-state battery according to another embodiment of the present invention. That is, as shown in FIG. 5, the present invention also provides an electrode assembly in which the configuration provided on the upper part of the anode layer (100) located at the center (in the stacking direction) is similarly provided on the lower part of the anode layer (100) located at the center, and which is vertically symmetrical with respect to the anode layer (100) located at the center (in the anode layer 100 in FIG. 5, the center is the anode current collector, and the comb-shaped parts provided on both sides of the center correspond to the anode active material layers).

[0028] That is, the length of the stacked negative electrode layers gradually decreases as they move upward and downward from the negative electrode layer included in the center of the electrode assembly, and the length of the stacked positive electrode layers gradually decreases as they move upward and downward from the negative electrode layer included in the center of the electrode assembly. The electrode assembly has a structure in which positive electrode layers and negative electrode layers are alternately stacked on each other on the upper and lower parts of the electrode assembly based on the negative electrode layer included in the center, and is symmetrical from the top to the bottom. The length of the negative electrode layer included in the center of the electrode assembly is longer than the length of the remaining negative electrode layers and the length of the positive electrode layers, and the upper and lower parts of the electrode assembly are pyramidal based on the negative electrode layer included in the center of the electrode assembly. In addition, when the upper and lower parts are symmetrical as in the electrode assembly shown in FIG. 5, it may be preferable to position the lower electrode assembly in the same shape as the upper electrode assembly, first apply isostatic pressure, and then turn it over and stack them in order.

[0029] In addition, as long as the short circuit phenomenon can be prevented or minimized through the electrode configuration of the present invention, the electrode assembly may be configured in various forms without any particular limitation. For example, the present invention also provides an electrode assembly in which a unit cell (one negative electrode layer (100) + one positive electrode layer (200)) is removed from each of the upper and lower parts as shown in FIG. 5 as an embodiment. The present invention also provides an electrode assembly in which a unit cell (one negative electrode layer (100) + one positive electrode layer (200)) is removed from only one of the upper and lower parts as shown in FIG. 5 as an embodiment. The present invention also provides an electrode assembly in which another unit cell (one negative electrode layer + one positive electrode layer) is further included in each of the upper and lower parts as shown in FIG. The present invention also provides an electrode assembly in which a unit cell (one negative electrode layer + one positive electrode layer) is further included in only one of the upper and lower parts as shown in FIG. Furthermore, it goes without saying that the contents described with reference to FIG. 3 and FIG. 4 are similarly applied to the other embodiments.

[0030] Next, the secondary battery according to the present invention will be described. The secondary battery includes the electrode assembly of the present invention described above and a storage case that houses the electrode assembly. And, the secondary battery is not particularly limited in terms of use. The secondary battery may be any battery that can accommodate the electrode assembly inside a storage case such as a pouch.

[0031] In the secondary battery according to the present invention, the positive electrode may contain a positive electrode active material, a conductive material, and a binder in a granular form. Among these, as the positive electrode active material, any material that can be used as the positive electrode active material of a lithium-ion secondary battery may be used without limitation. The positive electrode active material may be a lithium transition metal oxide containing at least one transition metal. For example, the positive electrode active material may be LiCoO2, LiNiO2, LiMnO2, Li2MnO3, LiMn2O4, Li(Ni a Co b Mn c )O2(0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), LiNi 1-y Co y O2(0 < y < 1), LiCo 1-y Mn y O2(0 < y < 1), LiNi 1-y Mn y O2(0 < y < 1), Li(Ni a Co b Mn c )O4(0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), LiMn 2-z Ni z O4(0 < z < 2), LiMn 2-z Co z O4(0 < z < 2) and those selected from the group consisting of combinations thereof.

[0032] The binder is mixed with the positive electrode active material and the conductive material, which are fine particles in a powder state, to bind the components together and aid in particle growth. For example, since the sulfide-based solid electrolyte has moisture-sensitive properties such as generating H2S gas when it comes into contact with moisture, it is preferable to remove moisture as much as possible from the time of forming the granules. The binder may be an organic binder, which means a binder that dissolves or disperses in an organic solvent, particularly N-methylpyrrolidone (NMP), and is distinguished from an aqueous binder that uses water as a solvent or dispersion medium. For example, the binder may be selected from the group consisting of polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polyimide, polyamideimide, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butylene rubber, and fluororubber, but is not limited thereto.

[0033] In the secondary battery according to the present invention, the solid electrolyte may include at least one selected from a sulfide-based solid electrolyte, a polymer-based solid electrolyte, and an oxide-based solid electrolyte, and may preferably include only a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may include a lithium salt, and the lithium salt may be Li + X - The anion of such a lithium salt is not particularly limited, but may be represented by F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P- , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - etc.

[0034] The sulfide-based solid electrolyte contains sulfur (S) and has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and may include Li-PS-based glass or Li-PS-based glass ceramic. Non-limiting examples of such sulfide-based solid electrolytes include Li2S-P2S5, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-LiCl-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, and Li2S-GeS2-ZnS, and the sulfide-based solid electrolyte may include at least one of these.

[0035] Such a solid electrolyte may function as a separator in a typical lithium secondary battery (i.e., electrically insulating the negative electrode and the positive electrode while allowing lithium ions to pass through). Meanwhile, the secondary battery may be used as a semi-solid battery by including a liquid electrolyte as necessary, in which case a separate polymer separator may be required.

[0036] In the secondary battery according to the present invention, the negative electrode may contain a negative electrode active material that can be used in a lithium ion secondary battery. For example, the negative electrode active material may be carbon such as graphitizable carbon or graphite-based carbon; Li x Fe2O3(0≦x≦1), Li x WO2(0≦x≦1), Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, elements of Group 1, Group 2, Group 3 of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8) and other metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4 and Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxides; lithium titanium oxides; etc. It may contain at least one selected from the group consisting of

[0037] Further, the present invention provides a battery module including the secondary battery as a unit cell, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include power tools powered by an electric motor; electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), etc.; electric two-wheelers including electric bicycles (E-bike) and electric scooters (E-scooter); electric golf carts; and power storage systems; etc., but are not limited thereto.

[0038] Below, preferred embodiments are shown to aid in understanding the present invention. However, these are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical spirit of the present invention. Naturally, these changes and modifications also fall within the scope of the appended claims.

[0039] [Example 1] Manufacture of secondary battery As shown in Fig. 3, a pyramid-shaped C-type bicell was fabricated in which a positive electrode layer having a positive electrode active material layer on each side thereof, a negative electrode layer was located on each side thereof, and a solid electrolyte layer was located between the positive electrode layer and the negative electrode layer. In this case, the length of the lower positive electrode active material layer was longer than that of the upper positive electrode active material layer, the length of the upper negative electrode layer was the same as that of the lower positive electrode active material layer, and the length of the lower negative electrode layer was longer than that of the lower positive electrode active material layer. The bicell was then placed on a metal plate and subjected to isostatic pressing (WIP).

[0040] [Comparative Example 1] Manufacture of secondary battery As shown in Figure 1, a typical C-shaped bicell was fabricated in which a cathode layer having a cathode active material layer on each side of the cathode current collector, an anode layer was located above and below the cathode layer, and a solid electrolyte layer was located between the cathode layer and the anode layer. The length of the lower cathode active material layer was the same as that of the upper cathode active material layer, the length of the upper anode layer was the same as that of the lower anode layer, and the length of the anode layer was longer than that of the cathode active material layer. The bicell was then placed on a metal plate and subjected to isostatic pressing (WIP).

[0041] [Experimental Example 1] Evaluation of battery charge / discharge The secondary batteries prepared in Example 1 and Comparative Example 1 were charged and discharged under the following conditions, while observing the battery state, and the life characteristics and capacity of the batteries were evaluated. The evaluation temperature was 25°C.

[0042] [Charge / discharge conditions] 0.1C 2 cycles, 0.1C / 0.33C 1 cycle, 0.1C / 0.5C 1 cycle, 0.1C / 1C 1 cycle, 0.1C / 0.1C 1 cycle, 0.1C / 0.33C cycle repeat (voltage range: 4.25V-3V)

[0043] As a result of observing the state of the battery while charging and discharging the battery as described above, it was confirmed that the battery manufactured in Example 1 operated normally, while the battery manufactured in Comparative Example 1 operated imperfectly due to a short circuit during charging. FIG. 6 is a graph comparing the life characteristics and capacity of secondary batteries manufactured in an embodiment of the present invention and a comparative example. As shown in FIG. 6, the battery manufactured in Comparative Example 1 did not charge or discharge normally due to a short circuit, while the battery manufactured in Example 1 was operated without a short circuit and was able to be normally charged and discharged. Therefore, it can be seen that when an electrode assembly or a battery includes an electrode configuration according to the present invention, unlike a normal battery, a short circuit does not occur during operation, and thus the performance of the battery is improved. [Explanation of symbols]

[0044] 10,100: Negative electrode layer (100a: negative electrode current collector, 100b: negative electrode active material layer) 20, 200: Positive electrode layer (200a: positive electrode current collector, 200b: first positive electrode active material layer, 200c: second positive electrode active material layer) 30,300: Metal plate

Claims

1. An electrode assembly in which a negative electrode layer having a negative electrode active material layer on both sides of a negative electrode current collector and a positive electrode layer having a first positive electrode active material layer and a second positive electrode active material layer on both sides of a positive electrode current collector are alternately laminated, and a solid electrolyte layer is interposed between the negative electrode layer and the positive electrode layer, the first and second positive electrode active material layers, which are extended from a center line of the positive electrode current collector toward both ends of the positive electrode current collector, have different lengths; The electrode assembly is characterized in that the length of the negative electrode active material layer facing the first positive electrode active material layer, which has a relatively short length, is equal to or shorter than the length of the second positive electrode active material layer, which has a relatively long length.

2. 2. The electrode assembly according to claim 1, wherein a length of the negative electrode active material layer facing the first positive electrode active material layer is equal to or longer than a length of the first positive electrode active material layer.

3. 2. The electrode assembly according to claim 1, wherein a length of the negative electrode active material layer facing the second positive electrode active material layer is equal to or longer than a length of the second positive electrode active material layer.

4. The electrode assembly of claim 1 , wherein the negative electrode active material layers provided on both sides of the negative electrode current collector have the same length.

5. 2. The electrode assembly of claim 1, wherein the negative active material layer facing the first positive active material layer and the second positive active material layer are not in contact with each other even after isostatic pressing.

6. The electrode assembly according to claim 5, wherein a length ratio of the second positive active material layer to the first positive active material layer is 1:0.3 to 0.

9.

7. The length of the stacked negative electrode layers gradually decreases from the negative electrode layer included in the center of the electrode assembly to the upper and lower portions.

6. The electrode assembly according to claim 5, wherein the lengths of the stacked positive electrode layers gradually decrease from the negative electrode layer included in the center of the electrode assembly to the upper and lower portions of the electrode assembly.

8. 8. The electrode assembly of claim 7, wherein a length of the negative electrode layer included in the center of the electrode assembly is longer than a length of the remaining negative electrode layers and a length of the positive electrode layer, and an upper and lower part of the electrode assembly are pyramidal based on the negative electrode layer included in the center of the electrode assembly.

9. A secondary battery comprising: the electrode assembly according to claim 1; and a storage case that houses the electrode assembly.

Images