Manufacturing method for all-solid-state batteries

Abstract

A method for manufacturing an all-solid-state battery is disclosed, which can suppress a short circuit phenomenon that occurs at the side portion during battery operation by isostatically pressing each unit cell and then stacking them. The method for manufacturing the all-solid-state battery includes the steps of: a) manufacturing a monocell or bicell by sequentially stacking a solid electrolyte and a positive electrode on one or both sides of a negative electrode; b) isostatically pressing the manufactured monocell or bicell; and c) stacking two or more of the isostatically pressed monocells or bicells, interposing a positive electrode current collector between one cell and the other cell, and bringing both sides of the interposed positive electrode current collector into contact with the positive electrode.

Description

[Technical Field]

[0001] This application claims priority under Korean Patent Application No. 10-2022-0132195 dated 14 October 2022, and all content disclosed in the said Korean Patent Application is incorporated herein as part of this specification.

[0002] The present invention relates to a method for manufacturing an all-solid-state battery, and more particularly to a method for manufacturing an all-solid-state battery that can suppress short-circuit phenomena occurring on the side surface during battery operation by stacking each unit cell after isotropically pressurizing it. [Background technology]

[0003] As technological development and demand for mobile devices and automobiles explode, more research is being conducted on secondary batteries with high energy density, discharge voltage, and excellent output stability. Examples of such secondary batteries include lithium-sulfur batteries, lithium-ion batteries, and lithium-ion polymer batteries. These secondary batteries can be classified into cylindrical, prismatic, and pouch-type based on their shape, and among these, interest in and demand for pouch-type battery cells are gradually increasing. Pouch-type battery cells can be stacked with a high degree of integration, have a high energy density per unit 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 pouch-type battery cells generally have a structure in which many unit cells, each containing a positive electrode, a negative electrode, and a separator membrane interposed between the positive and negative electrodes, are stacked (i.e., an electrode assembly or stack cell). After housing this electrode assembly in a battery case, an electrolyte can be injected, or a solid electrolyte can be provided within the electrode assembly from the beginning for commercialization (i.e., an all-solid-state battery).

[0005] Among these, all-solid-state batteries offer superior safety compared to other types of rechargeable batteries and are attracting particular attention in the fields of electric vehicles and mobile devices. In other words, all-solid-state batteries are batteries in which the electrolyte used in conventional lithium rechargeable batteries is replaced from liquid to solid. This eliminates the use of flammable solvents and completely prevents ignition or explosion due to the decomposition reaction of conventional electrolytes, thus significantly improving safety. In addition, all-solid-state batteries can use Li metal or Li alloy as the negative electrode material, which has the advantage of dramatically improving the energy density relative to the mass and volume of the battery.

[0006] Such all-solid-state batteries generally employ a warm isostatic pressing (WIP) process during manufacturing to ensure proper bonding between the electrode and solid electrolyte interface. This is because if the electrode-solid electrolyte interface is not properly bonded and the interface is not formed correctly, lithium (Li) ion movement becomes difficult, making battery operation impossible.

[0007] Figure 1 is a schematic side cross-sectional view showing the electrode stacking configuration of a typical all-solid-state battery. A typical all-solid-state battery generally has a configuration as shown in Figure 1, where a positive electrode (20, where 20a is the positive electrode current collector) shorter in length than the negative electrode (10) is positioned between the negative electrode (10, where 10a is the negative electrode current collector), and a solid electrolyte (30) is interposed between each of the negative electrode (10) and the positive electrode (20). Furthermore, in such a typical all-solid-state battery, for example, after sequentially stacking the negative electrode (10), solid electrolyte (30), positive electrode (20), solid electrolyte (30), and negative electrode (10), isotropic pressurization must be performed to bond the electrode-solid electrolyte interface once the stacking is complete.

[0008] However, since a normal all-solid-state battery has a structure as shown in FIG. 1 (that is, a structure in which a positive electrode is interposed between negative electrodes and the length of the positive electrode is shorter than the lengths of both negative electrodes), when isotropic pressure is applied simultaneously at the upper and lower parts with the same pressure, the both end parts (or side surfaces) of the upper and lower negative electrodes are bent. And in this process, cracks are likely to occur in the solid electrolyte layer and the negative electrode layer, and appropriate pressure cannot be applied to this part during battery driving, so conditions are likely to occur where lithium dendrite growth occurs, and a short circuit phenomenon occurs.

[0009] That is, in a conventional all-solid-state battery, isotropic pressure for interface bonding between the electrode and the solid electrolyte must be applied in a state where the lamination is completed. At this time, since a positive electrode is interposed between negative electrodes and at the same time the length of the positive electrode is shorter than the lengths of both negative electrodes, a short circuit phenomenon must occur between the end of the negative electrode and the side surface of the end of the positive electrode facing this during driving. Therefore, it is necessary to search for a solution that can eliminate the possibility of a short circuit phenomenon occurring during battery driving while applying isotropic pressure for interface bonding between the electrode and the solid electrolyte.

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, an object of the present invention is to provide a method for manufacturing an all-solid-state battery that can suppress a short circuit phenomenon occurring on the side surface during battery driving by laminating each unit cell after isotropically pressurizing it.

Means for Solving the Problems

[0011] To achieve the above object, the present invention provides a method for manufacturing an all-solid-state battery including the steps of: a) sequentially laminating a solid electrolyte and a positive electrode on each of one or both sides of a negative electrode to produce a monocell or a bicell; b) isotropically pressing the produced monocell or bicell; and c) laminating two or more of the isotropically pressed monocells or bicells with a positive electrode current collector interposed between one cell and another cell, and bringing both sides of the interposed positive electrode current collector into contact with the positive electrode respectively.

Advantages of the Invention

[0012] According to the method for manufacturing an all-solid-state battery of the present invention, since each unit cell is isotropically pressed before lamination, isotropic pressing is not required after lamination is completed. Thus, there is an advantage in that a short-circuit phenomenon occurring on the side surface during battery driving can be suppressed.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 15 is a schematic side cross-sectional view showing an electrode lamination form of a normal all-solid-state battery. [Figure 2] FIG. 18 is a schematic side cross-sectional view showing a state in which two isotropically pressed monocells are laminated with a positive electrode current collector interposed therebetween in an all-solid-state battery according to an embodiment of the present invention. [Figure 3] FIG. 21 is a schematic side cross-sectional view showing a state in which a plurality of isotropically pressed bicells are laminated with a positive electrode current collector interposed therebetween in an all-solid-state battery according to another embodiment of the present invention. [Figure 4] FIG. 24 is a graph comparing the life characteristics and capacity retention rates of secondary batteries manufactured according to an embodiment and a comparative example of the present invention.

Embodiments of the Invention

[0014] ​​​​​Figure 2 is a schematic side cross-sectional view showing how two isotropically pressurized monocells are stacked with a positive electrode current collector interposed between them in an all-solid-state battery according to one embodiment of the present invention, and Figure 3 is a schematic side cross-sectional view showing how a number of isotropically pressurized bicells are stacked with a positive electrode current collector interposed between them in an all-solid-state battery according to another embodiment of the present invention.

[0016] Referring to Figures 2 and 3, the method for manufacturing an all-solid-state battery according to the present invention includes the steps of: a) manufacturing a monocell (1000) or bicell (2000) by sequentially stacking a solid electrolyte (300) and a positive electrode (200) on one or both sides of a negative electrode (100); b) isotropically pressurizing the manufactured monocell (1000) or bicell (2000); and c) stacking two or more of the isotropically pressurized monocells (1000) or bicells (2000) with a positive electrode current collector (220) interposed between one cell and another, and bringing both sides of the interposed positive electrode current collector (220) into contact with the positive electrode (200).

[0017] Solid-state batteries offer superior safety compared to other types of rechargeable batteries and are attracting attention, particularly in the fields of electric vehicles and mobile devices. Essentially, a solid-state battery replaces the liquid electrolyte used in conventional lithium-ion batteries with a solid electrolyte. This eliminates the use of flammable solvents and completely prevents ignition or explosion due to the decomposition reaction of conventional electrolytes, significantly improving safety. Furthermore, solid-state batteries can use Li metal or Li alloy as the negative electrode material, offering the advantage of dramatically improving energy density relative to the battery's mass and volume. Such solid-state batteries generally employ a warm isostatic pressing (WIP) process during manufacturing to ensure proper bonding between the electrode and solid electrolyte interface. If the electrode-solid electrolyte interface is not properly bonded and formed, lithium (Li) ion movement becomes difficult, making battery operation impossible.

[0018] On the other hand, in a typical all-solid-state battery, as shown in Figure 1, a positive electrode (20, where 20a is the positive electrode current collector) is positioned between the negative electrode (10, where 10a is the negative electrode current collector), and the positive electrode (20, where 20a is the positive electrode current collector) is shorter in length than the negative electrode (10). This is to prevent the problem of lithium (Li) deposition in the sliding portion due to the difference in contact area between the positive and negative electrodes caused by the electrode sliding phenomenon. This lithium deposition problem can lead to a reduction in battery life and can even cause explosions and fires.

[0019] Furthermore, conventional all-solid-state batteries have a configuration in which a solid electrolyte (30) is interposed between the negative electrode (10) and the positive electrode (20). In addition, such conventional all-solid-state batteries require isotropic pressurization to bond the electrode-solid electrolyte interface after the stacking is complete, for example, by sequentially stacking the negative electrode (10), solid electrolyte (30), positive electrode (20), solid electrolyte (30), and negative electrode (10). However, conventional all-solid-state batteries have a structure as shown in Figure 1 (i.e., a positive electrode is interposed between negative electrodes, and the length of the positive electrode is shorter than the length of both negative electrodes), so when isotropic pressurization is performed by applying the same pressure simultaneously to the upper and lower parts, both ends (or sides) of the upper and lower negative electrodes are bent. During this process, cracks are likely to occur in the solid electrolyte layer and the negative electrode layer. Because appropriate pressure cannot be applied to these areas during battery operation, conditions are favorable for lithium dendrite growth, leading to a short circuit.

[0020] In other words, conventional all-solid-state batteries require isotropic pressurization for interfacial bonding between electrodes and solid electrolytes once the stacking is complete. At this time, the positive electrode is interposed between the negative electrodes, and the length of the positive electrode is shorter than the length of both negative electrodes. As a result, a short circuit inevitably occurs between the end of the negative electrode and the end side of the positive electrode opposite it during operation. However, the applicant has invented a method of stacking after isotropically pressurizing each unit cell (monocell or bicell) beforehand. In this case, isotropic pressurization is not required once the stacking is complete, thus suppressing the short circuit phenomenon that occurs at the side during battery operation.

[0021] To manufacture the all-solid-state battery according to the present invention, first, a monocell (1000) or bicell (2000) must be manufactured by sequentially stacking a solid electrolyte (300) and a positive electrode (or a positive electrode without a current collector or a free-standing positive electrode, 200) on one or both sides of a negative electrode (100) (step a). This is a necessary prerequisite for isotropic pressurization under conditions where there is absolutely no risk of a short circuit occurring between the positive and negative electrodes. In the case of a monocell (1000), it contains only one negative electrode (100) and one positive electrode (200), and isotropic pressurization is performed with the longest negative electrode (100) at the bottom, so there is no possibility of a short circuit occurring between the positive and negative electrodes even when they are electrically connected. In the case of a bicell (2000), the negative electrode (100) is composed of a single layer with negative electrode active material layers (100b) located on both sides of a negative electrode current collector (100a), and positive electrodes (200) are located on both sides of this layer. Therefore, even in this case, there is no possibility of a short circuit occurring between the positive and negative electrodes, even when they are electrically connected. On the other hand, both the positive electrode (200) contained in the monocell (1000) and the positive electrode (200) contained in the bicell (2000) must be freestanding positive electrodes that do not contain a positive electrode current collector.

[0022] Here, the structures of the monocell (1000) and bicell (2000) will be explained separately. The monocell (1000), as shown in Figure 2, has a structure in which a solid electrolyte (300) and a positive electrode (200) without a current collector are sequentially stacked on one side of a negative electrode (100). More specifically, the monocell (1000), as shown in Figure 2, has a structure in which a solid electrolyte (300) and a positive electrode (200) without a current collector are sequentially stacked on one side of a negative electrode active material layer (100b), and a negative electrode current collector (100a) may be attached to the other side of the negative electrode active material layer (100b). In other words, the negative electrode (100) of the monocell (1000) includes a negative electrode active material layer (100b) and a negative electrode current collector (100a) attached to one side of the negative electrode active material layer (100b), and the other side of the negative electrode active material layer (100b) has a structure in which a solid electrolyte (300) and a positive electrode (200) are sequentially stacked.

[0023] As shown in Figure 3, the bicell (2000) has a structure in which a solid electrolyte (300) and a positive electrode (200) without a current collector are sequentially stacked on each of the two sides of the negative electrode (100). More specifically, as shown in Figure 3, the bicell (2000) has a structure in which a solid electrolyte (300) and a positive electrode (200) without a current collector are sequentially stacked on each of the negative electrode active material layers (100b) located facing each other on both sides of the negative electrode current collector (100a). That is, the negative electrode (100) of the bicell (2000) includes a negative electrode current collector (100a); and negative electrode active material layers (100b) attached on both sides of the negative electrode current collector (100a); and each of the negative electrode active material layers (100b) has a structure in which a solid electrolyte (300) and a positive electrode (200) are sequentially stacked.

[0024] Furthermore, in both the monocell (1000) and bicell (2000), as shown in Figures 2 and 3, it is preferable that the length of the negative electrode (100) is longer than the length of the positive electrode (200) relative to the vertical cross-section. This is to prevent the problem of lithium deposition in the sliding portion due to the difference in contact area between the positive and negative electrodes caused by the electrode sliding phenomenon. This lithium deposition problem can lead to a reduction in battery life and even cause explosions and fires. On the other hand, although the above has been explained based on Figures 2 and 3, it can be said that monocells and bicells can be transformed into various structures and forms if the objectives of the present invention can be achieved.

[0025] As described above, after manufacturing a monocell (1000) or bicell (2000) by sequentially stacking a solid electrolyte (300) and a positive electrode (200) without a current collector on one or both sides of the negative electrode (100), the manufactured monocell (1000) or bicell (2000) is subjected to isotropic pressurization (step b). This is a process for bonding the interface between the electrode and the solid electrolyte, and as mentioned above, the isotropic pressurization is performed under conditions in which there is absolutely no risk of a short circuit occurring between the positive and negative electrodes. In the case of the monocell (1000), isotropic pressurization is performed in a simplified state in which the positive electrode (200) is located on top of the negative electrode (100), so that sufficient pressure can be applied and there is no room for a short circuit to occur between the positive and negative electrodes. In the case of the BiCell (2000), the negative electrode (100) is composed of a single layer with a negative electrode current collector (100a) flanked by negative electrode active material layers (100b) on both sides, and the positive electrode (200) is located on both sides of it. Therefore, even if isotropic pressure is applied, the negative electrode will not bend, and there is no possibility of a short circuit occurring between the positive and negative electrodes.

[0026] The isotropic pressing method may be any one selected from the group consisting of warm isotropic pressing (WIP), hot isotropic pressing (HIP), and cold isotropic pressing (CIP). Furthermore, it is preferable that these isotropic pressing methods be performed at a temperature within an appropriate range where interfacial contact between electrodes is well achieved through the molding of the solid electrolyte, and the electrode components are thermally stable. For example, warm isotropic pressing (WIP) may be performed at 45 to 100°C.

[0027] Furthermore, in order to stack isotropically pressurized monocells (1000) or bicells (2000) as shown in the next step, two or more monocells (1000) or bicells (2000) must each be prepared in an isotropically pressurized state. That is, when stacking monocells (1000) as unit cells, as shown in Figure 2, each of the two monocells (1000) must be prepared in an isotropically pressurized state. Also, when stacking bicells (2000) as unit cells, each of the bicells (2000) must be prepared in an isotropically pressurized state in a number that matches the scale of the desired all-solid-state battery. In other words, when stacking bicells (2000) as unit cells, there is no particular limit on the number of bicells (2000) that should be isotropically pressurized. Note that in Figure 3, a total of three bicells (2000) are stacked, so in this case, three isotropically pressurized bicells (2000) must be prepared. However, it should be noted that Figure 3 represents only one embodiment.

[0028] Finally, after isotropically pressurizing the monocell (1000) or bicell (2000) as described above, two or more of the isotropically pressurized monocells (1000) or bicells (2000) are stacked, with a positive electrode current collector (220) interposed between one cell and another, and both sides of the interposed positive electrode current collector (220) are brought into contact with the positive electrode (200) (without the current collector) (step c).

[0029] Specifically, when stacking the monocells (1000) as unit cells, as shown in Figure 2, the manufacturing of the all-solid-state battery can be completed by stacking a positive electrode current collector (220) on top of one monocell (1000), and then stacking the remaining monocell (1000) (the process of housing the battery inside a storage case such as a pouch may be performed separately). At this time, the two monocells (1000) are stacked with their respective "positive electrodes (200) without current collectors" facing each other, and both sides of the positive electrode current collector (220) interposed between them are in contact with each of the "positive electrodes (200) without current collectors".

[0030] When stacking the bicells (2000) as unit cells, as shown in Figure 3, the manufacturing of an all-solid-state battery can be completed by stacking a positive electrode current collector (220) on top of one bicell (2000), and then stacking the remaining bicell (2000) one more time (the process of housing the battery inside a storage case such as a pouch may be performed separately). There is no particular limit to the number of repetitions, and it may be set in various ways depending on the scale of the all-solid-state battery to be manufactured. In this case, the bicells (2000) are stacked with the "positive electrodes (200) without current collectors" contained in each of them facing each other, and both sides of the positive electrode current collector (220) interposed between them and each of the "positive electrodes (200) without current collectors" are in contact with each other.

[0031] Furthermore, when stacking bicells (2000) as unit cells, as shown in Figure 3, a positive electrode current collector (220) may be provided not only between one cell and another, but also at the outermost edge in the stacking direction of the battery, and in contact with the "positive electrode (200) without a current collector". In other words, when stacking two or more bicells (2000), a positive electrode current collector (220) may be provided at the outermost edge in the stacking direction of each, and in contact with the free-standing positive electrode (200). The positive electrode current collector (220) may be any material commonly used in the industry, such as aluminum foil.

[0032] Isotropic pressurization is not required during or after the lamination process (step c) described above. In other words, isotropic pressurization is not performed after step b) where the isotropic pressurization is performed. Isotropic pressurization for interfacial bonding between the electrode and solid electrolyte of the monocell (1000) or bicell (2000) has already been performed in step b), so there is no lithium ion movement problem, and during the lamination process in step c), bonding only occurs between the "positive electrode (200) without a current collector" and the positive electrode current collector (220) without interfacial bonding between the electrode and solid electrolyte, because even weak contact is sufficient for electron conduction in this bonding between the "positive electrode (200) without a current collector" and the positive electrode current collector (220).

[0033] Therefore, according to the manufacturing method of the all-solid-state battery according to the present invention, each unit cell containing the negative electrode in a single layer is isotropically pressurized before stacking, and isotropic pressurization is not required once stacking is complete. As a result, a short circuit between the negative electrodes does not occur during battery operation. In other words, during the manufacturing of the all-solid-state battery, both ends of the negative electrode (100) contained in either a monocell (1000) or a bicell (2000) maintain a constant distance from each other and from the respective side surfaces of both ends of the positive electrode (200) contained in the adjacent (facing) monocell (1000) or bicell (2000), thereby preventing a short circuit between the positive and negative electrodes during battery operation.

[0034] On the one hand, the all-solid-state battery manufactured by the manufacturing method of the all-solid-state battery according to the present invention may be housed in a storage case such as a pouch. And the all-solid-state battery has no particular limitation on its use. In the all-solid-state battery, 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 the all-solid-state battery may be used without limitation. The positive electrode active material may be a lithium transition metal oxide containing one or more transition metals. 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 may be selected from the group consisting of combinations thereof.

[0035] Furthermore, the binder is mixed together with the positive electrode active material and conductive material, which are fine particles in powder form, to bind the components together and help the particles grow. For example, sulfide-based solid electrolytes have properties that are sensitive to moisture, such as generating H2S gas when they come into contact with water, so it is preferable to remove as much moisture as possible from the time of granule formation. The binder may be an organic binder, and the organic binder means a binder that dissolves or disperses in an organic solvent, particularly N-methylpyrrolidone (NMP), and is distinguished from aqueous binders that use 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, polyamide-imide, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butylene rubber, and fluororubber, but is not limited to these.

[0036] In the all-solid-state battery described above, the solid electrolyte may contain one or more selected from sulfide-based solid electrolytes, polymer-based solid electrolytes, and oxide-based solid electrolytes, and it may be preferable to contain only a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may contain a lithium salt, and the lithium salt may be an ionizable lithium salt. + X - It can be represented as follows. While there are no particular limitations on the anions of such lithium salts, 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 - These are some examples.

[0037] Furthermore, the sulfide-based solid electrolyte contains sulfur (S) and has the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and may also include Li-PS glass or Li-PS 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 contain one or more of these.

[0038] Such a solid electrolyte may also serve a role similar to that of a separator membrane in a typical lithium secondary battery (i.e., electrically insulating the negative and positive electrodes while simultaneously allowing lithium ions to pass through). On the other hand, the all-solid-state battery may be used as a semi-solid-state battery by including a liquid electrolyte as needed, in which case an additional polymer separator membrane may be required.

[0039] In the all-solid-state battery, the negative electrode may contain a negative electrode active material that can be used in a normal all-solid-state 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., and may contain any one or more selected therefrom.

[0040] Further, the present invention provides a battery module including the all-solid-state 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-wheel vehicles including electric bicycles (E-bike) and electric scooters (E-scooter); electric golf carts; and power storage systems; etc., but are not limited thereto.

[0041] The following are preferred embodiments to aid in understanding the present invention, but these are merely illustrative examples, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and that these changes and modifications will naturally fall within the scope of the appended claims.

[0042] [Example 1] Manufacturing of all-solid-state batteries A monocell having a structure in which positive electrodes (freestanding positive electrodes) without a solid electrolyte and current collector are sequentially stacked on one side of the negative electrode was subjected to warm isotropic pressurization (WIP). Then, a positive electrode current collector was stacked on the other side of the freestanding positive electrode that does not face the solid electrolyte, and another monocell identical to the isotropically pressurized monocell was further stacked on top of it so that its freestanding positive electrode and positive electrode current collector face each other to manufacture an all-solid-state battery. In this case, the length of the negative electrode in the upper monocell and the length of the negative electrode in the lower monocell were configured to be the same, and the length of the freestanding positive electrode in the upper monocell and the length of the freestanding positive electrode in the lower monocell were the same, but shorter than the length of the negative electrode.

[0043] [Comparative Example 1] Manufacturing of all-solid-state batteries An all-solid-state battery was manufactured in the same manner as in Example 1, except that instead of performing warm isotropic pressurization (WIP) in the monocell state, warm isotropic pressurization (WIP) was performed after all stacking was completed (i.e., no isotropic pressurization was performed before stacking).

[0044] [Experimental Example 1] Evaluation of Battery Charge and Discharge The all-solid-state batteries manufactured in Example 1 and Comparative Example 1 were charged and discharged under the following conditions, and their state was observed. The battery life characteristics and capacity retention rate were also evaluated. The evaluation temperature was 25°C.

[0045] [Charge / discharge conditions] 0.1C charge / discharge (voltage range: 4.25V-3V, CV 0.05C)

[0046] As described above, by observing the state of the batteries while charging and discharging them, it was confirmed that the battery manufactured in Example 1 operated normally, while the battery manufactured in Comparative Example 1 experienced a short circuit during charging, confirming that the battery operated incompletely. Figure 4 is a graph comparing the life characteristics and capacity retention rates of secondary batteries manufactured according to one embodiment and a comparative example of the present invention. As shown in Figure 4, the battery manufactured in Comparative Example 1 did not perform charging and discharging normally due to the short circuit (i.e., a short circuit occurred at 10 cycles and the evaluation ended), while the battery manufactured in Example 1 was driven without a short circuit, allowing for normal charging and discharging. [Explanation of Symbols]

[0047] 10,100: Negative electrode (10a,100a: Negative electrode current collector, 100b: Negative electrode active material layer) 20: Positive electrode (20a: Positive electrode current collector) 200: Freestanding Cathode 220: Positive electrode current collector 30,300: Solid electrolyte 1000: Monocell 2000: BuySell

Claims

1. a) The step of manufacturing a monocell or bicell by sequentially stacking a solid electrolyte and a positive electrode on one or both sides of the negative electrode; b) The step of isotropically pressurizing the manufactured monocell or bicell; c) stacking two or more of the isotropically pressurized monocells or bicells, with a positive electrode current collector interposed between one cell and another, and bringing both sides of the interposed positive electrode current collector into contact with the positive electrode; In step b) above, the positive electrode included in the monocell and the positive electrode included in the bicell are free-standing positive electrodes that do not include a positive electrode current collector. A method for manufacturing an all-solid-state battery, characterized in that during the lamination of step c) above, bonding is performed only between the free-standing positive electrode and the positive electrode current collector, without interfacial bonding between the electrode and the solid electrolyte.

2. The method for manufacturing an all-solid-state battery according to claim 1, characterized in that isotropic pressurization is not performed after step b) above.

3. The method for manufacturing an all-solid-state battery according to claim 1, characterized in that the monocell and bicell are such that the length of all negative electrodes is longer than the length of all positive electrodes.

4. The method for manufacturing an all-solid-state battery according to claim 1, wherein in step b), the negative electrode of the monocell includes a negative electrode active material layer and a negative electrode current collector attached to one side of the negative electrode active material layer, and a solid electrolyte and a positive electrode are sequentially laminated on the other side of the negative electrode active material layer.

5. The method for manufacturing an all-solid-state battery according to claim 1, characterized in that, in step b), the negative electrode of the bicell includes a negative electrode current collector; and negative electrode active material layers attached on both sides of the negative electrode current collector, and a solid electrolyte and a positive electrode are sequentially laminated on each of the negative electrode active material layers.

6. The method for manufacturing an all-solid-state battery according to any one of claims 1 to 5, characterized in that the isotropic pressurization is selected from the group consisting of warm isotropic pressurization (WIP), hot isotropic pressurization (HIP), and cold isotropic pressurization (CIP).

7. The method for manufacturing an all-solid-state battery according to claim 1, characterized in that when stacking two or more of the aforementioned bicells, a positive electrode current collector is provided at each of the outermost layers in the stacking direction and is in contact with the free-standing positive electrode.

8. A method for manufacturing an all-solid-state battery according to any one of claims 1 to 5, characterized in that, during the manufacturing of the all-solid-state battery, both ends of the negative electrode contained in one of the monocells or bicells do not come into contact with the positive electrode contained in a monocell or bicell adjacent to the monocell or bicell.

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