All-solid-state batteries

Abstract

This disclosure provides an all-solid-state battery comprising an electrode stack including a positive electrode, an electrolyte membrane, and a negative electrode, and an electrode assembly including a pair of protective layers located on the positive electrode side and the negative electrode side of the electrode stack, respectively, and a separation membrane that wraps around the electrode assembly in a zigzag pattern, with the electrode assembly positioned in the folded portion.

Description

[Technical Field]

[0001] This invention claims priority under Korean Patent Application No. 10-2023-0102266 dated 4 August 2023, and all content disclosed in the documents of said Korean Patent Application is incorporated herein by reference.

[0002] This invention relates to an all-solid-state battery. More specifically, this disclosure relates to an all-solid-state battery in which a protective layer is further arranged on the outer casing of the electrode stack contained inside the all-solid-state battery, thereby preventing cracking of the electrolyte layer due to the tension of the separation membrane. [Background technology]

[0003] As technological development and demand for mobile devices and automobiles explode, more research is being conducted on rechargeable batteries with high energy density, discharge voltage, and excellent output stability. Examples of such rechargeable batteries include lithium-sulfur batteries, lithium-ion batteries, and lithium-ion polymer batteries. Furthermore, these rechargeable batteries can be classified into cylindrical, prismatic, and pouch types depending 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 one or more unit cells, each containing a positive electrode, a negative electrode, and a separator membrane interposed between them, are stacked (i.e., an electrode assembly or stack cell). After housing this electrode assembly in a battery case, an electrolyte is injected, or the product can be manufactured with a solid electrolyte already present in the electrode assembly from the beginning (i.e., an all-solid-state battery).

[0005] Among these, all-solid-state batteries are superior to other types of rechargeable batteries in terms of safety and are attracting attention, particularly 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. As a result, since no flammable solvent is used, ignition and explosion due to the decomposition reaction of conventional electrolytes do not occur at all, and safety can be greatly improved. In addition, all-solid-state batteries also have the advantage of being able to dramatically improve the energy density relative to the mass and volume of the battery, as lithium metal or lithium alloy may be used as the negative electrode material.

[0006] Among these all-solid-state batteries, sulfide-based all-solid-state batteries are the most commonly used. In the manufacturing process of these sulfide-based all-solid-state batteries, a warm isostatic pressing (WIP) process is generally applied to bond the electrode-solid electrolyte interface (i.e., electrodes, etc., are wrapped in a pouch, sealed, and then pressurized). If the electrode-solid electrolyte interface is not properly bonded and the interface is not formed correctly, the movement of lithium (Li) ions becomes difficult, and the battery cannot operate.

[0007] In this type of WIP process, as shown in Figure 1, there was a problem in that the electrolyte layer would crack even with a small impact after WIP.

[0008] In particular, as shown in Figure 2, when stacking cells using a Z-stacking method with a separation membrane, there is a problem of cracks occurring in the electrolyte layer due to the tension of the separation membrane. Therefore, it is necessary to explore novel all-solid-state batteries with a structure that does not cause cracks in the electrolyte layer even while the cells are isotropically pressurized. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Published Patent No. 10-2016-0131681 [Overview of the Initiative]

Problems to be Solved by the Invention

[0010] In order to solve the above problems, the inventors have proposed a solution. The object of the present disclosure is to provide a solid-state battery with a structure that can prevent the occurrence of cracks in the electrolyte layer where the size of the electrode dash is large due to the separation film when applying Z-stacking for the unit cell stack because the electrode / electrolyte layer becomes hard by the WIP process used when manufacturing the sulfide-based all-solid-state battery.

Means for Solving the Problems

[0011] To achieve the above object, in one embodiment of the present disclosure, an electrode assembly including an electrode laminate including a positive electrode, an electrolyte membrane, and a negative electrode and a pair of protective layers located on the upper and lower outer contours of the electrode laminate, and a separation film that wraps the electrode assembly in a zigzag manner and arranges the electrode assembly in the folded portion are provided.

[0012] Also, as the protective layer, an all-solid-state battery including any one material selected from the group consisting of PI, PP, and PET is provided.

[0013] Also, an all-solid-state battery in which the outside of the protective layer and the electrode laminate are joined via a primary coating layer or a binder layer is provided.

[0014] Also, as the binder layer, an all-solid-state battery including any one material selected from the group consisting of PVDF, PO, and PUR is provided.

[0015] Also, an all-solid-state battery in which the length of the protective layer is longer than that of the positive electrode and the negative electrode is provided.

[0016] Also, a positive electrode current collector is located on the positive electrode of the electrode assembly and on the separation film, and a negative electrode current collector is located on the negative electrode of the electrode assembly and on the separation film.

[0017] Furthermore, the separation membrane provides an all-solid-state battery that fixes the electrode assembly. [Effects of the Invention]

[0018] An all-solid-state battery according to one embodiment of the present disclosure has the effect of preventing cracks in the electrolyte layer due to the tension of the separation membrane by further arranging a protective layer on the outer casing of the electrode stack (positive electrode, electrolyte membrane, negative electrode). [Brief explanation of the drawing]

[0019] [Figure 1] This is a diagram showing the structure of a conventional all-solid-state battery. [Figure 2] This is a diagram showing the stacked structure of a conventional all-solid-state battery. [Figure 3] This is a drawing showing the cell structure of an all-solid-state battery according to one embodiment of the present disclosure. [Figure 4] This is a drawing showing a stacked structure of an all-solid-state battery according to one embodiment of the present disclosure. [Figure 5] This drawing shows a stacked structure of an all-solid-state battery according to another embodiment of the present disclosure. [Figure 6] This drawing shows a stacked structure of an all-solid-state battery according to another embodiment of the present disclosure. [Figure 7] This drawing shows a stacked structure of an all-solid-state battery according to another embodiment of the present disclosure. [Figure 8] This drawing shows a stacked structure of an all-solid-state battery according to another embodiment of the present disclosure. [Modes for carrying out the invention]

[0020] The following provides further details to aid in understanding this disclosure.

[0021] The terms and words used in this specification and in the claims should not be construed to be limited to their ordinary or dictionary meanings, but rather to be construed in a sense and concept consistent with the technical idea of ​​this disclosure, based on the principle that inventors may appropriately define the concepts of terms in order to best describe their inventions.

[0022] As used herein, the term “electrode stack” means a solid-state battery structure in which the positive electrode, electrolyte membrane, and negative electrode are simply stacked.

[0023] As used herein, the term "electrode assembly" means a solid-state battery structure that includes other additional components besides the electrode stack. For example, as used herein, it means a solid-state battery structure that further includes a protective layer in addition to the electrode stack.

[0024] Figure 3 is a diagram showing a unit cell of an all-solid-state battery according to one embodiment of the present disclosure.

[0025] Referring to Figure 3, an all-solid-state battery according to one embodiment of the present disclosure includes an electrode assembly comprising an electrode stack including a positive electrode, an electrolyte membrane, and a negative electrode, and a pair of protective layers located on the upper and lower outer casings of the electrode stack, and a separation membrane that wraps around the electrode assembly in a zigzag pattern, with the electrode assembly positioned in the folded portion.

[0026] An electrode assembly for an all-solid-state battery according to one embodiment of the present disclosure includes an electrode stack comprising a positive electrode (2), an electrolyte membrane (3), and a negative electrode (4).

[0027] An electrode stack according to one embodiment of the present disclosure may include a positive electrode (2).

[0028] The positive electrode according to one embodiment of the present disclosure may use a positive electrode without particular limitation as long as it is used in a all-solid-state battery. For example, it may contain a positive electrode active material, a solid electrolyte, a conductive material, and a binder. Among these, as the positive electrode active material, any material that can be used as the positive electrode active material of a all-solid-state battery may be used without particular 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, 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 combinations thereof may be selected from the group consisting of these.

[0029] 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 refers to 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), polyvinylidene 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 to these.

[0030] An electrode laminate according to one embodiment of the present disclosure may include an electrolyte membrane (3). The electrolyte membrane may include a solid electrolyte, and the solid electrolyte may include one or more selected from sulfide-based solid electrolytes, polymer-based solid electrolytes and oxide-based solid electrolytes, and it may be preferable to include only a sulfide-based solid electrolyte. The sulfide-based solid electrolyte may include a lithium salt, and the lithium salt may be an ionizable lithium salt Li + X - It may also be represented as follows. Such lithium salt anions are not particularly limited, but 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.

[0031] Furthermore, the sulfide-based solid electrolyte contains sulfur (S) and has 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.

[0032] Such a solid electrolyte can perform the same role as a separator 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 also be used as a semi-solid-state battery by including a liquid electrolyte as needed, in which case an additional polymer separator may be required.

[0033] The electrode laminate according to an embodiment of the present disclosure may include a negative electrode (4). The negative electrode may include 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 and 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, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), etc. 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 include any one or more selected from the above.

[0034] The electrode assembly of the all-solid-state battery according to an embodiment of the present disclosure includes a protective film (6).

[0035] When manufacturing a sulfide-based all-solid-state battery using the WIP process, the electrode / electrolyte layer may become hard. When stacking such hardened unit cells in the Z-stacking method, the tension of the wrapping separator can directly act on the electrode / electrolyte layer. At this time, the tension of the separator intensively acts on the electrolyte layer, which is larger in size than the electrode, and cracks may occur in the electrolyte layer due to the separator. At this time, since the protective film is disposed on the outer periphery of the electrode laminate, even if the separator wraps the electrode assembly and applies a strong pressure, it is impossible to directly apply pressure to the electrolyte film in the electrode assembly. Therefore, the electrode assembly of the all-solid-state battery according to an embodiment of the present disclosure can prevent cracks in such electrolyte films by providing a protective film.

[0036] For the functions described above, the protective layer of the all-solid-state battery according to one embodiment of the present disclosure may include any material that does not deform at a temperature of 80°C, for example, any one material selected from the group consisting of PI, PP, and PET.

[0037] In an all-solid-state battery according to one embodiment of the present disclosure, the protective layer and the outside of the electrode stack may be bonded via a primary coating layer or a binder layer.

[0038] In an all-solid-state battery according to one embodiment of the present disclosure, the primary coating layer may be a primary coating layer commonly used in the industry.

[0039] In an all-solid-state battery according to one embodiment of the present disclosure, the binder layer may be made of any material that has adhesive properties, and may include, for example, any one material selected from the group consisting of PVDF, PO, and PUR.

[0040] In an all-solid-state battery according to one embodiment of the present disclosure, the length of the protective layer may be longer than that of the positive and negative electrodes. Specifically, as shown in Figure 4, because the length of the protective layer is longer than that of the positive and negative electrodes, the separation membrane cannot directly apply pressure to the electrodes or electrolyte membrane. Therefore, cracking of the electrolyte membrane can be prevented.

[0041] In an all-solid-state battery according to one embodiment of the present disclosure, the lengths of the pair of protective layers may be the same. Specifically, as shown in Figure 4, when the lengths of the pair of protective layers are the same, they are longer than the positive and negative electrodes, so the separation membrane cannot directly apply pressure to the electrodes or electrolyte membrane. Therefore, cracking of the electrolyte membrane can be prevented.

[0042] An all-solid-state battery according to one embodiment of the present disclosure includes a separator membrane (7).

[0043] In an all-solid-state battery according to one embodiment of the present disclosure, the separation membrane can fix the electrode assembly. The separation membrane is not particularly limited as long as it is a general separation membrane used in secondary batteries, but preferably, a separation membrane made of one or more materials selected from the group consisting of polyethylene (PE), polypropylene (PP), and resins mixed with PE and PP may be used.

[0044] In an all-solid-state battery according to one embodiment of the present disclosure, a positive electrode current collector (1) may be located on the separator membrane between the positive electrode of the electrode assembly, and a negative electrode current collector (5) may be located on the separator membrane between the negative electrode of the electrode assembly.

[0045] In an all-solid-state battery according to one embodiment of the present disclosure, the electrode stack comprising a positive electrode (2), an electrolyte membrane (3), and a negative electrode (4) may have various structures.

[0046] In an all-solid-state battery according to one embodiment of the present disclosure, the electrode stack may have a cross-sectional electrode structure as shown in Figure 5. In an all-solid-state battery according to one embodiment of the present disclosure, a cross-sectional electrode may mean an electrode in which an electrode layer is formed only on one side of the current collector (foil).

[0047] In an all-solid-state battery according to one embodiment of the present disclosure, the electrode stack may have a C-type structure as shown in Figure 6. In an all-solid-state battery according to one embodiment of the present disclosure, a C-type structure may mean a structure in which an electrode with positive electrode layers formed on both sides of a current collector (foil) is placed in the center, and electrolyte layers and an electrode with a negative electrode layer formed on one side of the current collector (foil) are placed on both sides.

[0048] In an all-solid-state battery according to one embodiment of the present disclosure, the electrode stack may have an A-type structure as shown in Figure 7. In an all-solid-state battery according to one embodiment of the present disclosure, an A-type structure may mean a structure in which an electrode with negative electrode layers formed on both sides of a current collector (foil) is placed in the center, and electrolyte layers and electrodes with positive electrode layers formed on one side of the current collector (foil) are placed on both sides.

[0049] In an all-solid-state battery according to one embodiment of the present disclosure, the electrode stack may have a multi-unit cell structure as shown in Figure 8. In an all-solid-state battery according to one embodiment of the present disclosure, a multi-unit cell means one that uses more double-sided electrodes than a typical unit cell in order to improve energy density. For example, as shown in Figure 8, it may mean a structure in which an electrode with negative electrode layers formed on both sides of a current collector (foil) is placed in the center, an electrolyte layer and electrodes with positive electrode layers formed on both sides of the current collector (foil) are placed on either side of the center, and then an electrode with a negative electrode layer formed on one side of the current collector (foil) is placed on the outermost edge.

[0050] Furthermore, this disclosure provides a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source. Specific examples of the device include, but are not limited to, power tools powered by an electric motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and power storage systems.

[0051] Although this disclosure has been described above with reference to limited embodiments and drawings, it is understood that this disclosure is not limited thereto, and that various modifications and variations are possible within the equivalent scope of the technical concept of this disclosure and the claims set forth below by persons with ordinary skill in the art to which this disclosure pertains. [Explanation of symbols]

[0052] 1 Positive electrode current collector 2 Positive electrode 3 Electrolyte membrane 4 Negative electrode 5. Negative current collector 6. Protective layer 7. Separation membrane

Claims

1. An electrode assembly comprising an electrode laminate including a positive electrode, an electrolyte membrane, and a negative electrode, and a pair of protective layers located on the upper and lower outer casings of the electrode laminate, The system includes a separation membrane that encloses the electrode assembly in a zigzag pattern, and positions the electrode assembly in the folded portion. All-solid-state battery.

2. The all-solid-state battery according to claim 1, characterized in that the protective layer comprises one material selected from the group consisting of PI, PP, and PET.

3. The all-solid-state battery according to claim 1, characterized in that the protective layer and the outside of the electrode laminate are joined via a primary coating layer or a binder layer.

4. The all-solid-state battery according to claim 1, characterized in that the binder layer comprises one material selected from the group consisting of PVDF, PO, and PUR.

5. The all-solid-state battery according to claim 1, characterized in that the length of the protective layer is longer than that of the positive electrode and the negative electrode.

6. A positive electrode current collector is placed on the positive electrode and the separator membrane of the electrode assembly. The all-solid-state battery according to claim 1, characterized in that a negative electrode current collector is arranged on the negative electrode and the separator membrane of the electrode assembly.

7. The all-solid-state battery according to any one of claims 1 to 6, characterized in that the separation membrane fixes the electrode assembly.

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