Positive electrode for all-solid-state battery and all-solid-state battery including the same

Abstract

The present invention relates to a positive electrode for an all-solid-state battery, the positive electrode including a positive electrode active material, a fluorinated ionomer including a lithium-substituted sulfonate salt, a solid electrolyte, and conductive carbon, and an all-solid-state battery including the same.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0107946 dated August 17, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a positive electrode for an all-solid-state battery and an all-solid-state battery including the same. More specifically, the present invention relates to a positive electrode for an all-solid-state battery that has a simplified process and improved electrochemical properties and cycle characteristics, and an all-solid-state battery including the same. [Background technology]

[0003] The development of portable mobile electronic devices such as smartphones, MP3 players, and tablet PCs has led to an explosive increase in demand for secondary batteries capable of storing electrical energy. In particular, the emergence of electric vehicles, medium- to large-sized energy storage systems, and portable devices requiring high energy density has led to an increase in demand for lithium secondary batteries. In response to this increased demand for lithium secondary batteries, various research and development efforts are underway to improve the properties of the positive electrodes used in lithium secondary batteries.

[0004] Meanwhile, existing lithium secondary batteries use liquid non-aqueous organic electrolytes, which pose a risk of fire and explosion. In fact, explosions involving products using these electrolytes have been occurring on a continuous basis, making it urgent to resolve these issues.

[0005] An all-solid-state battery is a battery in which such organic electrolytes are replaced with solid electrolytes, and all of the components of the battery, such as the electrodes and electrolyte, are made of solids. Due to the high safety of the solid electrolyte itself, the risks of fire and explosion can be basically eliminated.

[0006] On the other hand, most solid electrolytes have lower ionic conductivity than liquid electrolytes, which results in lower battery capacity in practical applications and poorer cycle characteristics at room temperature than liquid electrolytes.

[0007] That is, although the use of a solid electrolyte can ensure the safety of the battery, it causes a problem of reduced cycle characteristics, and various studies are being conducted to solve this problem. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 5,523,179 Summary of the Invention [Problem to be solved by the invention]

[0009] One technical problem that the present application aims to solve is to provide a positive electrode for an all-solid-state battery in which the process is simplified and productivity is improved by producing the positive electrode without using a solvent, and an all-solid-state battery including the same.

[0010] Another technical problem to be solved by the present application is to provide a positive electrode for an all-solid-state battery, which has excellent binding properties between positive electrode active materials and has improved electrochemical properties and cycle properties by using a novel binder, and an all-solid-state battery including the same.

[0011] The technical problem to be solved by the present application is not limited to the above. [Means for solving the problem]

[0012] The present invention, which solves the above technical problems, provides an all-solid-state positive electrode and an all-solid-state battery including the same.

[0013] In one embodiment, the present invention includes a cathode for an all-solid-state battery, comprising a cathode active material, a perfluorinated ionomer including a lithium-substituted sulfonate salt, a solid electrolyte, and a conductive carbon.

[0014] In one embodiment, the fluorine-based ionomer may be represented by the following Chemical Formula 1:

[0015] [ka]

[0016] Each A is independently a substituted or unsubstituted C1 to C30 alkylene group, a substituted or unsubstituted C1 to C30 haloalkylene group, or a substituted or unsubstituted C1 to C30 hydroxyalkylene group, and n and m are each an integer of 1 to 100.

[0017] In one embodiment, in Formula 1, A is -(CF2-CF2) p and p can be an integer from 1 to 15.

[0018] In one embodiment, the positive electrode according to the present invention may be prepared by mixing the positive electrode active material, a fluorine-based ionomer containing lithium-substituted sulfonate, a solid electrolyte, and conductive carbon, without using a solvent.

[0019] In one embodiment, the positive electrode active material is LiCoO2, Li(Ni x Co y Mn z )O2[x+y+z=1], Li(Ni x Co y Al z )O2[x+y+z=1], and LiFePO4.

[0020] In one embodiment, the solid electrolyte may include a halide-based solid electrolyte or a sulfide-based solid electrolyte.

[0021] In one embodiment, the sulfide-based solid electrolyte is Li6PS5Cl, Li 10 GeP2S 12 , Li3PS4, and Li7P3S 11 The halide-based solid electrolyte may include one or more of Li3YCl6, Li3InCl6, and Li2ZrCl6.

[0022] In one embodiment, the conductive carbon may include at least one of vapor grown carbon fiber (VGCF), carbon nanotube (CNT), Super P, Super C, carbon black, Ketjen black, acetylene black, coke, glassy carbon, and activated carbon.

[0023] In one embodiment, the positive electrode according to the present invention may include 60% by weight to 95% by weight of the positive electrode active material, 5% by weight to 40% by weight of a solid electrolyte, 0.1% by weight to 10% by weight of a conductive carbon, and 0.1% by weight to 10% by weight of a fluorine-based ionomer.

[0024] In one embodiment, the fluorine-based ionomer is a copolymer containing polytetrafluoroethylene, and the fluorine-based ionomer may be present in an amount of 0.1% by weight to 5% by weight.

[0025] According to another aspect of the present invention, an embodiment of the present invention includes an all-solid-state battery including the above-described all-solid-state battery positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.

[0026] In one embodiment, the solid electrolyte layer may be made of the same material as the solid electrolyte contained in the positive electrode for the all-solid-state battery.

[0027] In one embodiment, the solid electrolyte and the solid electrolyte layer are Li6PS5Cl, Li 10 GeP2S 12 , Li3PS4, and Li7P3S 11 It may include one or more of the following:

[0028] In one embodiment, the negative electrode may include at least one of lithium metal and an indium-lithium alloy. [Effects of the Invention]

[0029] According to the present invention as detailed above, by using a novel fluorine-based ionomer to produce the positive electrode of the present invention, it is possible to provide a positive electrode for an all-solid-state battery having a high binding strength between positive electrode active materials without using a solvent, and an all-solid-state battery including the same.

[0030] In addition, the positive electrode for an all-solid-state battery and the all-solid-state battery including the same according to the present invention are provided to have ionic conductivity similar to that of a liquid electrolyte despite using a solid electrolyte, thereby improving battery capacity and cycle characteristics. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a diagram schematically illustrating a method for manufacturing a positive electrode for an all-solid-state battery by a solvent-free process using a positive electrode active material, a solid electrolyte, a conductive carbon, and a binder according to examples and comparative examples of the present invention. [Figure 2] 1 is a structural formula showing a binder included in an example and a comparative example of the present invention. [Figure 3] 1 is a schematic diagram of an all-solid-state battery manufactured using a composite positive electrode according to an example and a comparative example of the present invention. FIG. [Figure 4] 1 is a graph comparing charge / discharge curves at each cycle according to Comparative Example 1(a), Comparative Example 2(b), and Example 1(c) of the present invention. [Figure 5]1 is a graph showing cycle characteristics and efficiency according to Comparative Example 1(a), Comparative Example 2(b), and Example 1(c) of the present invention. [Figure 6] 1 is a graph showing the characteristics at each rate of Comparative Example 1, Comparative Example 2, and Example 1 of the present invention. [Figure 7] 1 shows the results of cycle characteristics of Example 1(a), Example 2(b), and Example 3(c) of the present invention. [Figure 8] 1 shows the results of cycle characteristics of Example 1(a), Example 4(b), Example 5(c), and Example 6(d). DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical concept of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete, and so that the concept of the present invention will be fully conveyed to those skilled in the art.

[0033] In this specification, when a component is referred to as being on another component, it means that it can be formed directly on the other component, or a third component can be interposed therebetween. Also, in the drawings, the thicknesses of films and regions are exaggerated for the purpose of effectively explaining the technical content.

[0034] Furthermore, although terms such as "first," "second," and "third" are used to describe various components in various embodiments of this specification, these components should not be limited by such terms. These terms are merely used to distinguish one component from another. Therefore, what is referred to as a "first component" in one embodiment may be referred to as a "second component" in another embodiment. Each embodiment described and exemplified herein also includes its complementary embodiment. Furthermore, in this specification, "and / or" is used to mean that at least one of the components listed before and after it is included.

[0035] In the specification, the singular includes the plural unless the context clearly dictates otherwise. Furthermore, the terms "comprise" or "have" are intended to specify the presence of features, numbers, steps, components or combinations thereof stated in the specification, and should not be understood as excluding the possible presence or addition of one or more other features, numbers, steps, components or combinations thereof.

[0036] Furthermore, in the following description of the present invention, if it is determined that a detailed description of related publicly known functions or configurations may unnecessarily obscure the gist of the present invention, such detailed description will be omitted.

[0037] Furthermore, in this specification, "mol %" is interpreted as meaning the content of any metal contained in a positive electrode active material or a positive electrode active material precursor, assuming that the total of the remaining metals, excluding sodium and oxygen, in the positive electrode active material or a positive electrode active material precursor is 100%.

[0038] One embodiment of the present invention may include a positive electrode for an all-solid-state battery, including a positive electrode active material, a perfluorinated ionomer including a lithium-substituted sulfonate salt, a solid electrolyte, and conductive carbon.

[0039] The positive electrode for the all-solid-state battery may be prepared by physically mixing a positive electrode active material, a fluorine-based ionomer, a solid electrolyte, and a conductive carbon without using a solvent, and the positive electrode active material, the solid electrolyte, and the conductive carbon may be bound to each other in a uniformly mixed state by the fluorine-based ionomer.

[0040] Typically, a cathode for an all-solid-state battery is prepared by uniformly mixing solid powders such as a cathode active material, a binder, a solid electrolyte, and conductive carbon in a solvent, dispersing the mixture in the solvent to form a slurry, and then fabricating the cathode. However, when fabricating a cathode using this solvent-based casting method, the solvent can react with the solid electrolyte, e.g., a sulfide-based solid electrolyte, to destroy the crystallinity of the solid electrolyte, thereby reducing ionic conductivity. Furthermore, when using a solvent, the selection of the binder type is limited, requiring that only polymer binders that are soluble in the solvent be used.

[0041] Meanwhile, the fluorine-based ionomer according to the present embodiment is a novel polymer binder, and since the fluorine-based ionomer has flexible properties, it can be easily mixed with the cathode active material, solid electrolyte, and conductive carbon during dry mixing without using a solvent. In addition, the fluorine-based ionomer contains a lithium-substituted sulfonate, which further improves the conductivity of lithium ions and thereby exhibits high capacity.

[0042] A positive electrode for an all-solid-state battery repeatedly contracts and expands due to the charge / discharge of lithium ions. However, the fluorine-based ionomer according to the present embodiment has flexible properties, and therefore, even when the contraction and expansion are repeated, the contact between the positive electrode active materials bound together by the fluorine-based ionomer can be easily maintained, thereby improving the life characteristics.

[0043] Specifically, the fluorine-based ionomer can be represented by the following Chemical Formula 1.

[0044] [ka]

[0045] Here, each A is independently a substituted or unsubstituted C1 to C30 alkylene group, a substituted or unsubstituted C1 to C30 haloalkylene group, or a substituted or unsubstituted C1 to C30 hydroxyalkylene group, and n and m are each an integer of 1 to 100. For example, the fluorine-based ionomer of Chemical Formula 1 may be a random copolymer.

[0046] More specifically, in the formula 1, A is -(CF2-CF2) p -, where p is an integer from 1 to 15.

[0047] For example, the fluorine-based ionomer may be a polytetrafluoroethylene-based copolymer polymer represented by the following Chemical Formula 2, which may contain lithium ions, and specifically may be poly(tetrafluoroethylene-co-perfluoro(3-oxa-4-pentenesulfonic acid) lithium salt.

[0048] [ka]

[0049] Here, n can be an integer of 1 to 100, and m can be an integer of 1 to 20. Specifically, n can be an integer that is 5 times m. More specifically, it can be a random copolymer in which n is 5 and m is 1.

[0050] The positive electrode active material may be prepared by calcining a composite metal hydroxide containing at least one of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al) with a lithium compound. For example, the positive electrode active material may have a layered structure and may exhibit high capacity by containing a high content of nickel (50% or more).

[0051] The positive electrode active material is LiCoO2, Li(Ni x Co y Mn z )O2[x+y+z=1], Li(Ni x Co y Alz)O2[x+y+z=1], and LiFePO4.

[0052] The positive electrode for the all-solid-state battery according to this embodiment may include a solid electrolyte, and the solid electrolyte may include a halide-based solid electrolyte or a sulfide-based solid electrolyte. For example, the sulfide-based solid electrolyte may include Li6PS5Cl, Li 10 GeP2S 12 , Li3PS4, and Li7P3S 11 The halide-based solid electrolyte may include one or more of Li3YCl6, Li3InCl6, and Li2ZrCl6.

[0053] The solid electrolyte may be mixed with a positive electrode active material to further improve ion mobility, and may be a sulfide-based solid electrolyte.

[0054] The conductive carbon may include at least one of vapor grown carbon fiber (VGCF), carbon nanotube (CNT), Super P, Super C, carbon black, Ketjen black, acetylene black, coke, glassy carbon, and activated carbon.

[0055] In one embodiment of the present invention, the positive electrode according to the present invention may include 60 wt % to 95 wt % of the positive electrode active material, 5 wt % to 40 wt % of a solid electrolyte, 0.1 wt % to 10 wt % of a conductive carbon, and 0.1 wt % to 10 wt % of a fluorine-based ionomer.

[0056] Specifically, the fluorine-based ionomer is a copolymer containing polytetrafluoroethylene, and the fluorine-based ionomer may be present in an amount of 0.1% by weight to 5% by weight. More specifically, the fluorine-based ionomer may be 0.1 wt% or more, 0.2 wt% or more, 0.3 wt% or more, 0.4 wt% or more, 0.5 wt% or more, 0.6 wt% or more, 0.7 wt% or more, 0.8 wt% or more, 0.9 wt% or more, or 1.0 wt% or more, or 5.0 wt% or less, 4.9 wt% or less, 4.8 wt% or less, 4.7 wt% or less, 4.6 wt% or less, 4.5 wt% or less, 4.4 wt% or less, 4.3 wt% or less, 4.2 wt% or less, 4.1 wt% or less, 4.0 wt% or less, 3.9 wt% or less, 3.8 wt% or less, 3.7 wt% or less, 3.6 wt% or less, 3.5 wt% or less, 3.4 wt% or less, 3.3 wt% or less, 3.2 wt% or less, 3.1 wt% or less, or 3.0 wt% or less. If the content of the fluorine-based ionomer is less than 0.1 wt%, the amount is too small to adequately bind the positive electrode active material, which can be a problem. If the content exceeds 5 wt%, the electron and ion conductivity within the positive electrode may be reduced, or the content of the positive electrode active material may be unnecessarily reduced, resulting in a decrease in capacity.

[0057] According to another aspect of the present invention, an embodiment of the present invention includes an all-solid-state battery including the above-described all-solid-state battery positive electrode, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.

[0058] The solid electrolyte layer may be made of the same material as the solid electrolyte contained in the positive electrode for the all-solid-state battery. By using the same material for the solid electrolyte contained in the positive electrode for the all-solid-state battery and the solid electrolyte layer, it is possible to improve the mobility of lithium ions, stabilize the overall structure of the all-solid-state battery, and improve production efficiency.

[0059] The solid electrolyte and the solid electrolyte layer are made of Li6PS5Cl, Li 10 GeP2S 12 , Li3PS4, and Li7P3S 11 The sulfide-based solid electrolyte may include at least one of the following:

[0060] The positive electrode for the all-solid-state battery according to the present embodiment is prepared without using a solvent using the fluorine-based ionomer, thereby preventing the solvent remaining in the positive electrode for the all-solid-state battery from reacting with the sulfide-based solid electrolyte to reduce the crystallinity of the solid electrolyte. The negative electrode may be made of at least one of lithium metal and an indium-lithium alloy.

[0061] EXAMPLES Hereinafter, examples and comparative examples of the present invention will be described. However, the following examples are merely preferred examples of the present invention, and the scope of the present invention is not limited to the following examples.

[0062] 1. Manufacturing of cathodes for all-solid-state batteries FIG. 1 is a diagram schematically illustrating a method for manufacturing a positive electrode for an all-solid-state battery by a solventless process using a positive electrode active material, solid electrolyte, conductive carbon, and binder according to examples and comparative examples of the present invention. FIG. 2 is a structural formula showing the binders included in the examples and comparative examples of the present invention. In FIG. 2, a is a polytetrafluoroethylene copolymer ionomer binder according to Examples 1 to 6 (where n = 5, m = 1), b is a nitrile butadiene rubber binder according to Comparative Example 1 (where n = 3, m = 1), and c is a polytetrafluoroethylene binder according to Comparative Example 2. FIG. 3 is a schematic diagram of an all-solid-state battery manufactured using a composite positive electrode according to an example and comparative example of the present invention.

[0063] Example 1 LiNi, which contains 70% nickel, 15% cobalt, and 15% manganese 0.7 Co 0.15 Mn 0.15 A cathode active material of O2 (hereafter referred to as NCM) was mixed with a sulfide-based solid electrolyte, Li6PS5Cl, at room temperature. A conductive material (VGCF, Sigma-Aldrich) and a polytetrafluoroethylene copolymer ionomer binder (see Figure 2a) were then added to the cathode active material / solid electrolyte mixture and dry mixed for 10 minutes to fabricate a composite cathode. The cathode active material, sulfide-based solid electrolyte, conductive material, and binder were mixed in the weight ratios shown in Table 1 below. The composite cathode was pressurized at 430 MPa. An anode current collector (copper), a lithium-indium alloy (lithium: Honjo, indium: Nilaco), a solid electrolyte layer of Li6PS5Cl (100 mg), a composite cathode, and a cathode current collector (aluminum) were stacked in this order to fabricate an all-solid-state battery, as shown in Figure 3. Here, the loading levels of the composite positive electrodes are shown in Table 1 below.

[0064] Example 2 A composite positive electrode was prepared in the same manner as in Example 1, but when an all-solid-state battery was fabricated, the loading level of the composite positive electrode was lower than that of Example 1 as shown in Table 1 below.

[0065] Example 3 A composite positive electrode was prepared in the same manner as in Example 1, but when an all-solid-state battery was fabricated, the loading level of the composite positive electrode was higher than that of Example 1 as shown in Table 1 below.

[0066] Example 4 A composite cathode was prepared in the same manner as in Example 1, except that the content of the polytetrafluoroethylene-based copolymer ionomer binder was reduced and the content of the solid electrolyte was increased as shown in Table 1. An all-solid-state battery was prepared using the prepared composite cathode at the same loading level as in Example 1.

[0067] Example 5 A composite cathode was prepared in the same manner as in Example 1, except that the content of the polytetrafluoroethylene-based copolymer ionomer binder was increased and the content of the solid electrolyte was decreased as shown in Table 1. An all-solid-state battery was prepared using the prepared composite cathode at the same loading level as in Example 1.

[0068] Example 6 A composite cathode was prepared in the same manner as in Example 1, except that the content of the polytetrafluoroethylene-based copolymer ionomer binder was increased and the content of the solid electrolyte was decreased as shown in Table 1. An all-solid-state battery was prepared using the prepared composite cathode at the same loading level as in Example 1.

[0069] Comparative Example 1 LiNi, which contains 70% nickel, 15% cobalt, and 15% manganese, was dissolved in xylene (Sigma Aldrich). 0.7 Co 0.15 Mn 0.15The cathode active material, O2 (hereafter referred to as NCM), and the sulfide-based solid electrolyte, Li6PS5Cl, were mixed at room temperature. The conductive material (Super-P) and nitrile butadiene rubber binder (Poly(acrylonitrile-co-butadiene), Sigma-Aldrich Co., Ltd.; see Figure 2b) were then added to the xylene solvent, cathode active material, and solid electrolyte mixture, followed by dry mixing at room temperature for 10 minutes to fabricate a composite cathode. The cathode active material, sulfide-based solid electrolyte, conductive material, and binder were mixed in the weight ratios shown in Table 1 below. As shown in Figure 3, lithium metal (Honjo Co., Ltd.), a solid electrolyte layer of Li6PS5Cl (100 mg), and the resulting composite cathode were stacked in this order. The composite cathode was then dried in an oven at 100°C for 12 hours to remove the solvent, resulting in the fabrication of an all-solid-state battery. The loading levels of the composite cathode are shown in Table 1 below. The methods and products not specifically described in Comparative Example 1 were prepared in the same manner as in Example 1.

[0070] Comparative Example 2 A composite cathode was fabricated in the same manner as in Example 1, except that polytetrafluoroethylene (Sigma-Aldrich, see FIG. 2c) was used as the binder. An all-solid-state battery was fabricated using the fabricated composite cathode at the same loading level as in Example 1.

[0071] [Table 1]

[0072] 2. Evaluation of Electrochemical Performance Evaluation of ionic conductivity After preparing the mixture of solid electrolyte and binder according to Comparative Examples 1 and 2 and Example 1, 100 mg of the mixture was pressurized at 300 MPa to prepare pellets. Stainless steel electrodes were attached to both of the prepared pellets, and the ionic conductivity was measured at room temperature using an impedance analyzer (ZIVE MP1, Wontech Co., Ltd.). Table 2 compares the type and composition of the solid electrolyte and binder used in the composite positive electrodes of Comparative Examples 1 and 2 and Example 1, as well as their respective ionic conductivities. Comparative Examples 1, 2, and Example 1 differ only in the type of binder, and the binder and solid electrolyte contents constituting the composite positive electrodes are the same, with a solid electrolyte:binder weight ratio of 25:2. Without the binder, the ionic conductivity of the Li6PS5Cl solid electrolyte itself is 1.67 mS cm. -1 When a polymer binder is included as in Comparative Examples 1 and 2 and Example 1, the ionic conductivity is 1.67 mS cm -1 It can be seen that the value is lower.

[0073] When the nitrile butadiene rubber binder used in Comparative Example 1 was included, the -1 , and 1.31 mS cm when the polytetrafluoroethylene binder used in Comparative Example 2 was included. -1 , and 1.45 mS cm when the polytetrafluoroethylene copolymer ionomer binder used in Example 1 was included. -1 That is, it can be confirmed that when a polytetrafluoroethylene copolymer ionomer binder containing lithium ions is used as in Example 1, higher ionic conductivity is exhibited compared to when using existing binders.

[0074] [Table 2]

[0075] Capacity and cycle characteristics evaluation At 30°C, 4.3V charging at 0.5C (1.153mA) and 3.0V (vs Li / Li + ) discharge, charge-discharge cycles were performed, and the voltage and capacity were measured at each cycle.

[0076] 4 is a graph comparing the charge-discharge curves at each cycle for Comparative Example 1a, Comparative Example 2b, and Example 1c of the present invention. In Comparative Example 1, Comparative Example 2, and Example 1, the other conditions were the same, and only the type of binder was different. The capacities were confirmed at 1 cycle, 10 cycles, 20 cycles, 50 cycles, and 100 cycles.

[0077] Comparative Example 1, which used a nitrile butadiene rubber binder, exhibited lower initial capacity than Comparative Example 2 and Example 1, and exhibited a decrease in capacity and an increase in overvoltage as cycling progressed. Comparative Example 2, which used a polytetrafluoroethylene binder, used a solventless process, and exhibited reduced damage to the solid electrolyte compared to Comparative Example 1, resulting in an increase in initial capacity, but exhibited a decrease in capacity and an increase in overvoltage as cycling progressed. Example 1, which used a polytetrafluoroethylene-based copolymer ionomer binder, exhibited a higher initial capacity than Comparative Examples 1 and 2, and was maintained with almost no increase in overvoltage or almost no capacity loss as cycling progressed. It was confirmed that Example 1 and Comparative Example 1 exhibited high initial capacity because the composite positive electrode was fabricated using a solventless process, preventing crystalline damage to the solid electrolyte or electrolyte membrane due to the solvent. It was confirmed that Example 1, when using a polytetrafluoroethylene-based copolymer ionomer binder in the composite positive electrode, exhibited superior cycle characteristics compared to Comparative Examples 1 and 2. It is believed that in Example 1, the binding strength between the positive electrode active materials is maintained well even when the positive electrode reversibly contracts and expands as charging and discharging proceeds, allowing lithium ions to move efficiently.

[0078] 5 is a graph showing the cycle characteristics and efficiency of Comparative Example 1a, Comparative Example 2b, and Example 1c of the present invention. Charge-discharge cycles were performed at 30°C, 0.5C (1.153 mA), charging to 4.3V, and discharging to 3.0V (vs. Li / Li+).

[0079] Comparing Comparative Examples 1 and 2, it can be seen that Comparative Example 2 exhibits superior discharge capacity and cycle characteristics compared to Comparative Example 1. This is because Comparative Example 2 fabricated the composite cathode using a solventless process, while Comparative Example 1 fabricated the composite cathode using a wet process using a solvent, which can affect the discharge capacity and cycle characteristics. Specifically, the solvent contained in the composite cathode during the fabrication process can react with the solid electrolyte. Therefore, Comparative Example 1 used a xylene solvent with sufficiently low polarity, and the polymer binder also used a material with low polarity. As a result, Comparative Example 1, which used a high-loading cathode, exhibited poor discharge capacity and cycle characteristics.

[0080] Comparing Comparative Example 2 and Example 1, it can be seen that in both cases, composite positive electrodes were prepared without using a solvent, and Example 1 exhibited superior cycle characteristics compared to Comparative Example 2. This is believed to be because the polytetrafluoroethylene-based copolymer ionomer binder in Example 1 effectively binds the positive electrode active material, conductive material, and solid electrolyte, which is maintained during cycling, and the lithium ions contained in the polytetrafluoroethylene-based copolymer ionomer binder improve the mobility of lithium ions.

[0081] That is, when a composite positive electrode is manufactured using a binder that allows for a solvent-free dry process, the discharge capacity and cycle characteristics are improved, and it can be confirmed that excellent cycle characteristics are maintained, particularly when a polytetrafluoroethylene copolymer ionomer binder is used as in Example 1.

[0082] 6 is a graph showing the rate characteristics of Comparative Example 1, Comparative Example 2, and Example 1. Each was charged and discharged five times at 0.1C, 0.2C, 0.5C, 1.0C, and 2.0C, followed by another five times at 0.1C.

[0083] In the case of Comparative Example 1, it was confirmed that the capacity decreased as the charge / discharge current density increased, and that almost no capacity development occurred at high rates of 1.0 C or higher. In the case of Comparative Example 2, it was confirmed that even at 1.0 C, a superior capacity was exhibited compared to Comparative Example 1, but at a high rate of 2.0 C, a significant decrease in discharge capacity was observed. It was confirmed that Example 1 exhibited superior rate-specific characteristics compared to Comparative Examples 1 and 2, and even at a high rate of 2.0 C, there was almost no capacity decrease, demonstrating excellent characteristics. In other words, it was confirmed that Example 1 can be applied to high-rate / high-speed charge / discharge in all-solid-state batteries, and that output characteristics are improved.

[0084] 7 shows the results of the cycle characteristics of Examples 1a, 2b, and 3c of the present invention. In Examples 1, 2, and 3, the polytetrafluoroethylene copolymer ionomer binder was applied in the same amount of 2 wt %, but the loading level of the positive electrode was 22.4 mg / cm. 2 (Example 1), 11.2 mg / cm 2 (Example 2), and 30.0 mg / cm 2 This is a different result from Example 3. Comparing Examples 1a, 2b, and 3c, it can be seen that the discharge capacity and cycle characteristics are maintained at an excellent level even when the loading level is increased.

[0085] 8 shows the cycle characteristics of Examples 1a, 4b, 5c, and 6d. In Examples 1, 4, 5, and 6, the loading level of the composite positive electrode was 22.4 mg / cm. 2The results are for the same battery as Example 1, but with the same polytetrafluoroethylene-based copolymer ionomer binder added at different contents. Example 4b contains 0.1 wt% polytetrafluoroethylene-based copolymer ionomer binder, a lower binder content than Example 1 (2 wt%), and it was confirmed that the overvoltage increased and the capacity decreased during cycling. Examples 5c and 6d contain 5 wt% and 10 wt% polytetrafluoroethylene-based copolymer ionomer binder, respectively, and showed better cycle characteristics than Example 4, but relatively lower cycle characteristics than Example 1. That is, it was confirmed that a binder content of 2 wt% was the best for the composite positive electrode system like Example 1.

[0086] Those skilled in the art will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential characteristics thereof. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not limiting. The scope of the present invention is defined by the claims that follow rather than the above detailed description, and all modifications and variations that fall within the meaning and scope of the claims and their equivalents should be construed as being within the scope of the present invention.

Claims

1. positive electrode active material, perfluorinated ionomers containing lithium substituted sulfonates; a solid electrolyte, and conductive carbon, The fluorine-based ionomer is a positive electrode for an all-solid-state battery represented by the following chemical formula 1. 【Chemistry 1】 Each A is independently a substituted or unsubstituted C1 to C30 alkylene group, a substituted or unsubstituted C1 to C30 haloalkylene group, or a substituted or unsubstituted C1 to C30 hydroxyalkylene group, and n and m are each an integer of 1 to 100.

2. In the above Chemical Formula 1, The A is -(CF ２ -CF ２ ) ｐ -, and p is an integer of 1 to 15. The positive electrode for an all-solid-state battery according to claim 1 .

3. 2. The positive electrode for an all-solid-state battery according to claim 1, which is a dry mixture comprising the positive electrode active material, a fluorine-based ionomer containing a lithium-substituted sulfonate, a solid electrolyte, and conductive carbon.

4. The positive electrode active material is LiCoO ２ , Li(Ni ｘ Co ｙ Mnz)O ２ [x+y+z=1], Li(Ni ｘ Co ｙ Alz)O ２ [x+y+z=1], and LiFePO ４ The positive electrode for an all-solid-state battery according to claim 1 , comprising any one or more of:

5. 2. The positive electrode for an all-solid-state battery according to claim 1, wherein the solid electrolyte comprises a halide-based solid electrolyte or a sulfide-based solid electrolyte.

6. The sulfide-based solid electrolyte is Li ６ P.S. ５ Cl, Li １０ GeP ２ S １２ , Li ３ P.S. ４ , and Li ７ P ３ S １１ including one or more of the following: The halide-based solid electrolyte is Li ３ YCl ６ , Li ３ InCl ６ , and Li ２ ZrCl ６ The positive electrode for an all-solid-state battery according to claim 5 , comprising any one or more of:

7. 2. The positive electrode for an all-solid-state battery of claim 1, wherein the conductive carbon comprises at least one of vapor grown carbon fiber (VGCF), carbon nanotube (CNT), carbon black, acetylene black, coke, glassy carbon, and activated carbon.

8. 2. The positive electrode for an all-solid-state battery according to claim 1, comprising 60% by weight to 90% by weight of the positive electrode active material, 5% by weight to 35% by weight of a solid electrolyte, 0.1% by weight to 10% by weight of conductive carbon, and 0.1% by weight to 10% by weight of a fluorine-based ionomer.

9. the fluorine-based ionomer is a copolymer containing polytetrafluoroethylene, The positive electrode for an all-solid-state battery according to claim 8, comprising the fluorine-based ionomer in an amount of 0.1% by weight to 5% by weight.

10. The positive electrode for an all-solid-state battery according to any one of claims 1 to 9, a negative electrode, and a solid electrolyte layer interposed between the positive electrode and the negative electrode.

11. 11. The all-solid-state battery according to claim 10, wherein the solid electrolyte layer is made of the same material as the solid electrolyte contained in the positive electrode for the all-solid-state battery.

12. The solid electrolyte and the solid electrolyte layer are ６ P.S. ５ Cl, Li １０ GeP ２ S １２ , Li ３ P.S. ４ , and Li ７ P ３ S １１ The all-solid-state battery according to claim 10, comprising any one or more of:

13. The all-solid-state battery of claim 10, wherein the negative electrode comprises at least one of lithium metal and an indium-lithium alloy.

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