Lead tab for joining electrode tab and all-solid-state battery including a structure in which the lead tab is joined to the electrode tab

Abstract

The present invention discloses a lead tab for joining an electrode tab, which can solve the problem of detachment of a negative electrode protective layer by joining a lead tab of a specific material to an electrode tab with low welding energy, and an all-solid-state battery including a structure in which the lead tab and electrode tab are joined, in which the electrolyte does not come into contact with the lead tab and a lithiation reaction does not occur. The lead tab for joining an electrode tab is joined to an electrode tab of an electrode assembly for an all-solid-state battery to form a joint, and the lead included in the joint contains aluminum.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0104686 filed on August 10, 2023, and Korean Patent Application No. 10-2024-0105049 filed on August 7, 2024, and incorporates all contents disclosed in the documents of said Korean patent applications as part of this specification.

[0002] The present invention relates to a lead tab for joining an electrode tab and an all-solid-state battery including a structure in which the lead tab is joined to an electrode tab, and more specifically, to a lead tab for joining an electrode tab and an all-solid-state battery including a structure in which the lead tab made of a specific material is joined to the electrode tab with low welding energy, which can solve the problem of detachment of the negative electrode protective layer, and in which the lead tab and the electrode tab are joined together, the electrolyte does not come into contact with the lead tab and no lithiation reaction occurs. [Background technology]

[0003] As interest in energy storage technology grows, its application fields have expanded to include mobile phones, tablets, laptops, and video cameras, as well as the energy sources for electric vehicles (EVs) and hybrid electric vehicles (HEVs), and research and development of electrochemical devices is gradually increasing. Electrochemical devices are the field that has received the most attention in this regard, and the development of secondary batteries that can be charged and discharged has become a focus of attention. Recently, the development of such batteries has led to research and development of new electrode and battery designs to improve capacity density and specific energy.

[0004] During the manufacture of such secondary batteries, welding is performed to connect tabs between unit electrodes to obtain output suited to the intended application, and a process of joining the electrode tab and lead tab is also performed. FIG. 1 is a perspective view showing the joined electrode tab and lead tab in a typical secondary battery, and FIG. 2 is a plan view of the lead tab joined to the electrode tab in the typical secondary battery. As shown in FIG. 1, a typical secondary battery requires an electrode tab (positive electrode tab or negative electrode tab, 2) to electrically connect the positive electrode plate and the negative electrode plate constituting the electrode assembly 1 to an external device. This electrode tab 2 is joined by welding to a lead tab (positive electrode lead tab or negative electrode lead tab, 3) as shown in FIG. 2. As shown in FIG. 2, the lead tab 3 includes a metal lead 3a and a lead film 3b located locally on one or both sides of the metal lead 3a, and the metal lead 3a located on one side is joined so as to overlap the electrode tab.

[0005] More specifically, most secondary batteries use ultrasonic welding, laser welding, or resistance welding to join the negative electrode tab (copper) or positive electrode tab (aluminum) that extends from the electrode of the electrode assembly and protrudes outward to a separate lead tab (copper, nickel). For example, in lithium-ion batteries, the negative electrode tab is made of copper (Cu) and then welded to the lead tab (Ni) to join the electrode tab and lead tab.

[0006] Meanwhile, all-solid-state batteries, which are safer than lithium secondary batteries due to the risk of explosion, replace liquid electrolytes with solid ones. This eliminates the need for flammable solvents and eliminates the risk of fires or explosions caused by the decomposition of conventional electrolytes, significantly improving safety. All-solid-state batteries can use lithium metal or lithium alloys as the anode material, significantly improving the battery's energy density per mass and volume. Furthermore, a protective layer (specifically, a layer between the anode active material and the solid electrolyte to prevent contact between them) is located on the surface of such lithium metal anodes. However, when the anode tab and lead tab (copper or nickel) are welded together, the anode protective layer can detach. This is because high welding energy is applied in an environment that would otherwise weaken the adhesion between the anode and anode protective layer. Therefore, a solution is needed to prevent the anode protective layer from detaching when the electrode tab and lead tab are welded together. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a lead tab for joining an electrode tab, which can solve the problem of detachment of a negative electrode protective layer by joining a lead tab made of a specific material to an electrode tab with low welding energy, and an all-solid-state battery including a structure in which the lead tab and electrode tab are joined, in which the electrolyte does not come into contact with the lead tab and no lithiation reaction occurs. [Means for solving the problem]

[0008] To achieve the above object, the present invention provides a lead tab for joining an electrode tab, which is joined to an electrode tab of an electrode assembly for an all-solid-state battery to form a joint, and is characterized in that a lead included in the joint contains aluminum.

[0009] The present invention also provides an all-solid-state battery having a structure including a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode, and in which the lead tab is joined to an electrode tab. [Effects of the Invention]

[0010] According to the lead tab for electrode tab joining and the all-solid-state battery including a structure in which the lead tab is joined to an electrode tab according to the present invention, the lead tab made of a specific material can be joined to the electrode tab with low welding energy, thereby solving the problem of detachment of the negative electrode protective layer, and thus providing an advantage of increasing the assembly stability of the battery.

[0011] Furthermore, the lead tab for joining an electrode tab according to the present invention and the all-solid-state battery including a structure in which the lead tab is joined to an electrode tab have the advantage that the electrolyte does not come into contact with the lead tab in the all-solid-state battery including a structure in which the lead tab and electrode tab are joined, and therefore no lithiation reaction occurs. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a state in which an electrode tab and a lead tab are joined in a typical secondary battery. [Figure 2] FIG. 2 is a plan view of a lead tab joined to an electrode tab in a typical secondary battery. [Figure 3] FIG. 2 is a plan view showing an electrode tab and a lead tab joined together in a secondary battery. [Figure 4] 1 is a graph showing the performance of batteries according to an example of the present invention and a comparative example. [Figure 5] 1 is a graph showing the life performance of a battery according to an embodiment of the present invention. [Figure 6] 10 is a graph showing the life performance of a battery according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below.

[0014] The lead tab for joining an electrode tab according to the present invention is joined to an electrode tab of an electrode assembly for an all-solid-state battery to form a joint, and the lead included in the joint contains aluminum.

[0015] Generally, when manufacturing secondary batteries, welding is performed to connect tabs between unit electrodes to obtain the output required for the intended purpose, and this requires a process of joining a regular lead tab, as shown in Figure 2, to an electrode tab, as shown in Figure 1, by welding. Most secondary batteries generally use ultrasonic welding, laser welding, or resistance welding to join the negative electrode tab (copper) or positive electrode tab (aluminum) to the lead tab (copper, nickel). For example, lithium-ion batteries use copper (Cu) as the negative electrode tab and weld it to the lead tab (Ni) to join the electrode tab and lead tab.

[0016] Meanwhile, all-solid-state batteries, which are safer than lithium secondary batteries and pose less of a risk of explosion, replace liquid electrolytes with solid ones. These batteries have the advantage of dramatically improving the energy density per unit mass and volume of the battery because they can use lithium metal or lithium alloys as the anode material. Furthermore, a protective layer is placed on the surface of these lithium metal anodes. However, when the anode tab and lead tab (copper or nickel) are welded together, the anode protective layer can detach. This is because high welding energy is applied in an environment that weakens the adhesive strength between the anode and anode protective layer.

[0017] Therefore, the present applicant has discovered a method for preventing peeling of the anode protective layer by welding the electrode tab and the lead tab together, by including aluminum in the lead included in the joint formed by joining the electrode tab of the electrode assembly for a solid-state battery. Hereinafter, the lead tab for joining the electrode tab according to the present invention will be described in more detail.

[0018] The lead constituting the lead tab for joining an electrode tab according to the present invention is in a sheet form, similar to conventional leads, and can be joined or adhered to an electrode tab to form a joint. The lead constituting the lead tab for joining an electrode tab according to the present invention and joining the electrode tab (corresponding to reference numeral 2 in FIG. 1) to form a joint corresponds to reference numeral 3a in FIG. 2. Conventionally, the lead of a lead tab has been made of copper or nickel, but in this case, in conventional all-solid-state batteries, a problem occurs in which the negative electrode protective layer peels off when the negative electrode tab and the lead tab are joined by welding. However, the present applicant has solved the problem of negative electrode protective layer peeling by using aluminum for the lead tab, allowing it to be joined to the electrode tab with low welding energy.

[0019] That is, the lead tab for electrode tab joining of the present invention is joined to an electrode tab of an electrode assembly for an all-solid-state battery to form a joint, and the lead included in the joint contains aluminum, and the lead may contain aluminum in an amount of 50 to 100 wt %, preferably 70 to 100 wt %, more preferably 85 to 100 wt %, and most preferably 95 to 100 wt %, based on the total weight of the lead.

[0020] Furthermore, the lead may have a structure or form in which one metal is plated onto the surface of another metal, for example, a form in which aluminum is plated onto the surface of a metal such as copper, manganese, silicon, magnesium, zinc, and nickel.

[0021] And, when the lead contains aluminum in an amount of less than 100% by weight based on the total weight of the lead, the lead may further contain an element selected from the group consisting of copper, manganese, silicon, magnesium, zinc and nickel (here, this means a uniformly mixed state, not plated).

[0022] As described above, the lead tab for joining an electrode tab of the present invention is preferably a lead tab for joining a negative electrode tab, but can also be used for joining a positive electrode tab, if necessary. That is, the lead tab for joining an electrode tab may be used for joining one or more of a positive electrode tab and a negative electrode tab. In particular, in consideration of the ease of the joining process, it may be preferable to use the lead tab for joining an electrode tab for joining both a positive electrode tab and a negative electrode tab at the same time.

[0023] Meanwhile, the lead tab for joining an electrode tab according to the present invention is also characterized in that it does not come into contact with the electrolyte contained in the electrode assembly, which will be described in detail in the section "All-Solid-State Battery" below.

[0024] Furthermore, the lead tab for joining an electrode tab of the present invention may further include a lead film (3b) locally located on one or both sides of the lead (3a), as shown in Figure 2. The lead film may be made of the same material as the lead film contained in a normal lead tab, such as polypropylene.

[0025] The electrode tab of the "electrode assembly for an all-solid-state battery" is preferably an electrode tab of an electrode assembly for a sulfide-based all-solid-state battery.

[0026] Next, the all-solid-state battery according to the present invention will be described.

[0027] The all-solid-state battery has a structure in which the lead tabs are joined to electrode tabs. More specifically, the all-solid-state battery includes the lead tabs, including a positive electrode lead tab joined to a positive electrode tab and a negative electrode lead tab joined to a negative electrode tab, and at least one of the positive electrode lead tab and the negative electrode lead tab is joined to the electrode tab using aluminum. The all-solid-state battery is preferably a sulfide-based all-solid-state battery.

[0028] In one embodiment of the present invention, the all-solid-state battery may be manufactured including a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode. And the all-solid-state battery may be manufactured by a known method with a configuration known in this field.

[0029] The positive electrode may contain an active material, a conductive material, and a binder in a granular form or the like. As the positive electrode active material, any material that can be used as the positive electrode active material of a normal lithium-ion secondary battery may be used without limitation. And 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.

[0030] The positive electrode conductive material may also be used without particular limitation as long as it can be used as the positive electrode conductive material of a normal lithium-ion secondary battery. For example, the positive electrode conductive material may be a normal material such as carbon nanotubes (single-walled carbon nano tube, multi-walled carbon nano tube) or carbon black.

[0031] The positive electrode binder is mixed together with the positive electrode active material and the positive electrode conductive material, and binds each component to assist the growth of particles. 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 an aqueous binder using 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 fluorine rubber, but is not limited thereto. And the weight ratio of the positive electrode active material, the positive electrode conductive material, and the binder contained in the positive electrode also applies the normal one.

[0032] The negative electrode may contain a negative electrode active material that can be used in a normal lithium ion secondary battery. For example, the negative electrode active material is carbon such as non-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) 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 any one or more selected from the above.

[0033] Solid electrolytes in solid-state batteries can be broadly classified into organic (polymer) solid electrolytes and inorganic solid electrolytes, and inorganic solid electrolytes can be divided into sulfide and oxide types. Currently, the solid electrolyte with the most advanced technological development is the sulfide solid electrolyte, and development has progressed to the point where ionic conductivity is close to that of organic electrolytes. Thus, sulfide solid electrolytes are among the top 10 solid electrolytes. -3 S / cm~10 -2 Not only does it have high ionic conductivity of S / cm, but it also has excellent thermal stability and ductility, which allows it to make good contact with the interface, which is advantageous for improving resistance (interfacial compatibility).

[0034] Although all of the above-mentioned solid electrolytes can be applied to the present invention, sulfide-based solid electrolytes are more preferred. The sulfide-based solid electrolyte may contain a lithium salt, and the lithium salt may be an ionizable lithium salt, such as Li + X - The anion of such a lithium salt is not particularly limited, but may be 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.

[0035] The sulfide-based solid electrolyte contains sulfur (S) and has 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 one or more of these. Furthermore, the sulfide-based solid electrolyte contained as a base material in the solid electrolyte for an all-solid-state battery of the present invention is not limited to these and may be composed of a material that constitutes a typical sulfide-based solid electrolyte.

[0036] Meanwhile, research conducted by the present applicant has revealed that contact between an aluminum-containing lead and an electrolyte can cause a lithiation reaction, rendering the battery inoperable. Therefore, the present applicant has attempted to prevent the lithiation reaction by preventing contact between the lead tab for joining the electrode tab in an all-solid-state battery and the solid electrolyte. More specifically, the present applicant has solved this problem by positioning the end of the lead tab joining the electrode tab at a distance of 1.1 to 5 times, preferably 1.2 to 3 times, and more preferably 1.5 to 2.5 times the average distance between the end of the electrode and the end of the electrolyte from one end of the electrode assembly from which the electrode tab is pulled out.

[0037] 3 is a plan view showing the state in which an electrode tab and a lead tab are joined in a secondary battery. Referring to FIG. 3, the end position of the lead tab in the direction of joining with the electrode tab will be described in more detail. The end position of the lead tab (3a) in the direction of joining with the electrode tab refers to a position spaced from the end of the electrode (5) in the direction in which the electrode tab (2) is drawn out by the distance (S1 in FIG. 3) between the end of the electrode (5) and the end of the lead tab (3a). Furthermore, the average distance (S2 in FIG. 3) between the end of the electrode (5) and the end of the electrolyte (7) refers to the sum of the maximum and minimum distances between the end of the electrode (5) and the end of the electrolyte (7), divided by two.

[0038] The present invention also 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, but are not limited to, power tools powered by an electric motor, electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs), electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters, electric golf carts, and power storage systems.

[0039] Preferred examples will be described below to aid in understanding the present invention. However, the following examples 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 idea of ​​the present invention. Naturally, such changes and modifications also fall within the scope of the appended claims.

[0040] [Example 1] Production of all-solid-state battery First, an electrode assembly was fabricated by stacking unit cells, each consisting of a positive electrode containing a lithium transition metal oxide as the positive electrode active material, a lithium metal negative electrode, and a solid electrolyte (Li6PS5Cl) sandwiched between them. The end of the lead tab that would join with the electrode tab was positioned twice the average distance between the end of the electrode and the end of the electrolyte from the tip of the electrode assembly from which the electrode tab was pulled out. Next, aluminum leads were attached to the positive and negative electrode tabs, respectively.

[0041] Comparative Example 1: Production of an all-solid-state battery An all-solid-state battery was produced in the same manner as in Example 1, except that nickel leads were joined to both the negative electrode tab and the positive electrode tab instead of aluminum leads.

[0042] Comparative Example 2: Production of an all-solid-state battery An all-solid-state battery was produced in the same manner as in Example 1, except that the end of the lead tab in the direction joining with the electrode tab was positioned at a distance equal to the average distance between the end of the electrode and the end of the electrolyte from one tip of the electrode assembly from which the electrode tab was pulled out, so that the electrolyte membrane was in contact with the lead.

[0043] [Experimental Example 1] Performance evaluation of all-solid-state batteries The all-solid-state batteries prepared in Example 1 and Comparative Examples 1 and 2 were operated under the following charge-discharge conditions with an operating voltage range of 4.25 V to 3.0 V and an operating temperature of 60° C., and the performance was evaluated during the first cycle (FIG. 4) or 100 cycles (FIGS. 5 and 6). The results are shown in FIGS. 4 to 6.

[0044] -Charging conditions: 0.1C, 4.25V CC / CV, 0.05C cut-off -Discharge conditions: 0.1C, 3.0V, CC

[0045] Fig. 4 is a graph showing the performance of batteries according to an example of the present invention and a comparative example, Fig. 5 is a graph showing the lifespan performance of a battery according to an example (Example 1) of the present invention, and Fig. 6 is a graph showing the lifespan performance of a battery according to a comparative example (Comparative Example 1). As a result of evaluating the performance of the all-solid-state batteries manufactured in Example 1, Comparative Examples 1 and 2, as shown in Fig. 4, the all-solid-state battery of Example 1, which used an aluminum lead and did not contact the electrolyte membrane with the lead, was able to perform normal charging and discharging, unlike the all-solid-state battery of Comparative Example 2, which used an aluminum lead but did contact the electrolyte membrane with the lead.

[0046] Meanwhile, the all-solid-state battery of Comparative Example 1, which used a nickel lead and did not have contact between the electrolyte membrane and the lead, also showed similar performance in the first cycle as Example 1. However, as can be seen from the comparison and contrast of Figures 5 and 6, the all-solid-state battery of Comparative Example 1 rapidly deteriorated in performance as the cycles increased due to performance deviation caused by damage to the anode. Therefore, it can be seen that the object of the present invention can be achieved only by using an aluminum lead and not having contact between the electrolyte and the lead.

Claims

1. A lead tab for joining an electrode tab, which is joined to an electrode tab of an electrode assembly for an all-solid-state battery to form a joint, characterized in that a lead included in the joint contains aluminum.

2. 2. The lead tab for joining an electrode tab according to claim 1, wherein the lead contains aluminum in an amount of 50 to 100 wt % based on the total weight of the lead.

3. 3. The lead tab for joining electrode tabs according to claim 2, wherein when the lead contains aluminum in an amount of less than 100% by weight based on the total weight of the lead, the lead further comprises an element selected from the group consisting of copper, manganese, silicon, magnesium, zinc, and nickel.

4. 2. The lead tab for joining an electrode tab according to claim 1, wherein the lead has a form in which a surface of a metal selected from the group consisting of copper, manganese, silicon, magnesium, zinc, and nickel is plated with aluminum.

5. The lead tab for joining an electrode tab according to claim 1 , wherein the lead tab is used for joining a positive electrode tab or a negative electrode tab.

6. The lead tab for joining electrode tabs according to claim 5 , wherein the lead tab is simultaneously applied for joining positive electrode tabs and negative electrode tabs.

7. The lead tab for joining an electrode tab according to claim 1 , wherein the electrode tab of the electrode assembly for an all-solid-state battery is an electrode tab of an electrode assembly for a sulfide-based all-solid-state battery.

8. 8. An all-solid-state battery comprising a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode, wherein the lead tab according to claim 1 is joined to an electrode tab.

9. 10. The all-solid-state battery of claim 8, wherein the all-solid-state battery includes a positive electrode lead tab joined to a positive electrode tab and a negative electrode lead tab joined to a negative electrode tab, and at least one of the positive electrode lead tab and the negative electrode lead tab is joined to the electrode tab using aluminum.

10. The all-solid-state battery according to claim 8 , wherein a lead tab included in the all-solid-state battery is not in contact with an electrolyte.

11. 9. The all-solid-state battery according to claim 8, wherein an end of the lead tab in a direction joining with the electrode tab is located 1.1 to 5 times the average distance between an end of the electrode and an end of the electrolyte from one end of the electrode assembly from which the electrode tab is pulled out.

12. The all-solid-state battery according to claim 8 , wherein the all-solid-state battery is a sulfide-based all-solid-state battery.

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