KR102813878B1 - Positive electrode comprising insulating layer having excellent wet adhesion and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a positive electrode for a lithium secondary battery including an insulating layer having excellent wet adhesiveness, and a lithium secondary battery including the same. The insulating layer has an advantage in that it has excellent wet adhesiveness in an electrolyte, thereby preventing the movement of lithium ions in an overlay region of the electrode, thereby suppressing capacity expression, etc.

Description

{POSITIVE ELECTRODE COMPRISING INSULATING LAYER HAVING EXCELLENT WET ADHESION AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a positive electrode for a lithium secondary battery including an insulating layer having excellent wet adhesion, a method for manufacturing the same, and a lithium secondary battery including the same.

As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, much research is being conducted on batteries that can meet various needs.

In terms of battery shape, there is a high demand for square batteries and pouch-type batteries that can be applied to products such as mobile phones due to their thin thickness, and in terms of materials, there is a high demand for lithium secondary batteries such as lithium cobalt polymer batteries that have excellent energy density, discharge voltage, and safety.

One of the major research tasks in these secondary batteries is to improve safety. The main cause of safety-related accidents in batteries is due to abnormal high temperature conditions caused by short circuits between the positive and negative electrodes. In other words, under normal circumstances, the separator between the positive and negative electrodes is located to maintain electrical insulation, but under abnormal circumstances such as overcharge or overdischarge of the battery, dendritic growth of electrode materials or internal short circuit caused by foreign substances, sharp objects such as nails or screws piercing the battery, or excessive deformation of the battery due to external force, the existing separator shows its limitations.

In general, the separator is mainly a microporous membrane made of polyolefin resin, but its heat resistance is insufficient as its heat resistance temperature is about 120 to 160℃. Therefore, when an internal short circuit occurs, the separator shrinks due to the short circuit reaction heat, the short circuit area expands, and a thermal runaway state occurs in which a larger amount of reaction heat is generated. This phenomenon mainly occurs at the electrode active material-coated end of the electrode current collector coated with the electrode active material when stacking electrodes, and various methods have been attempted to reduce the possibility of a short circuit of the electrode under external impact or at high temperatures.

Specifically, in order to solve the internal short circuit of the battery, a method has been proposed of forming an insulating layer by attaching an insulating tape to a part of the non-conductive part and the active material layer of the electrode, or by coating an insulating liquid. For example, a method has been proposed of applying a binder for insulating purposes to a part of the non-conductive part and the active material layer of the positive electrode, or of coating an insulating liquid (hereinafter, an insulating layer) in which a mixture of the binder and inorganic particles is dispersed in a solvent.

Meanwhile, the electrode in an actual secondary battery exists in a state of being immersed in an electrolyte, but the adhesive strength (hereinafter, wet adhesive strength) of the conventional insulating layer in a state of being immersed in an electrolyte is reduced, so that the movement of lithium ions in the overlay region of the electrode is not prevented, resulting in a problem of capacity development (see Fig. 1). In particular, lithium ions may be precipitated when capacity is developed in the overlay region of the electrode, which may cause a decrease in the stability of the battery cell.

Therefore, there is a need to develop an insulating layer with excellent wet adhesion.

Republic of Korea Patent Publication No. 10-2019-0093524

Accordingly, the purpose of the present invention is to provide a positive electrode for a lithium secondary battery including an insulating layer having excellent wet adhesion, a method for manufacturing the same, and a lithium secondary battery including the same.

In order to solve the above-described problem, the present invention comprises, in one embodiment, a current collector; an active material layer formed on one or both sides of the current collector, the active material layer including a positive electrode active material, a conductive material, and a non-aqueous binder; and an insulating layer positioned on a side of the active material layer. In addition, the insulating layer is formed of an aqueous binder substituted with a non-aqueous solvent.

In one embodiment, the insulating layer is positioned on the current collector, and is structured to cover a portion of the active material layer applied to the current collector from a portion of the non-conductive portion of the current collector.

In one specific embodiment, the insulating layer is positioned on the current collector and has a structure formed to cover a part of the sliding area of the active material layer applied to the current collector from a part of the non-conductive portion of the current collector, and the formation height of the insulating layer is in a range of 10 to 50% of the height of the active material layer.

In another embodiment, the insulating layer is positioned on the current collector, and has a structure formed to cover a part of the sliding area of the active material layer applied to the current collector from a part of the non-conductive portion of the current collector, and the formation height of the insulating layer is in a range of 50 to 100% of the height of the active material layer.

For example, the thickness of the insulating layer is in the range of 1 ㎛ to 50 ㎛ on average.

In one embodiment, the insulating layer further comprises inorganic particles dispersed in an aqueous binder substituted with a non-aqueous solvent. In addition, a weight ratio of the inorganic particles and the aqueous binder is in a range of 1:99 to 95:5.

The above inorganic particles may be at least one selected from the group consisting of AlOOH, Al ₂ O ₃ , γ-AlOOH, Al(OH) ₃ , Mg(OH) ₂ , Ti(OH) ₄ , MgO, CaO, Cr ₂ O ₃ , _{MnO 2} , Fe ₂ O ₃ , Co _{3 O 4 ,} NiO, ZrO ₂ , BaTiO ₃ , SnO ₂ , CeO 2 , Y ₂ O ₃ , SiO ₂ , silicon carbide (SIC) and boron nitride (BN).

In addition, the aqueous binder may be at least one selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluoroelastomer, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose.

In addition, the non-aqueous binder of the active material layer may be at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropene (PVDF-co-HFP, Poly(vinylidene fluoride-co-hexafluoropropene)), poly(ethylene oxide) (PEO, Poly(ethylene oxide)), polyacrylic acid (PAA), polyimide (PI), polyamideimide (PAI), and polyimide-polyamideimide copolymer (PI-PAI).

In a specific example, the non-aqueous binder may be polyvinylidene fluoride (PVDF). Additionally, the aqueous binder may be an aqueous binder substituted with a non-aqueous organic solvent, for example, styrene-butadiene rubber substituted with an N-methyl-2-pyrrolidone solvent.

Meanwhile, in addition, in one embodiment of the present invention, the insulating layer may also have a composition including both an aqueous binder substituted with a non-aqueous solvent and a non-aqueous binder. For example, the insulating layer may have a composition in which the aqueous binder and the non-aqueous binder are mixed in a weight ratio of 20:80 to 80:20, or a composition in which the aqueous binder and the non-aqueous binder are mixed in a weight ratio of 40:60 to 60:40.

Furthermore, the present invention provides a lithium secondary battery including the positive electrode for a secondary battery described above.

A positive electrode for a lithium secondary battery including an insulating layer having excellent wet adhesion according to the present invention and a lithium secondary battery including the same have the advantage that the insulating layer has excellent wet adhesion in an electrolyte, thereby preventing the movement of lithium ions in an overlay region of the electrode, thereby suppressing capacity expression, etc.

Figure 1 is a schematic diagram showing the movement of lithium ions in the overlay region of the electrode.
Figure 2 is a flow chart showing a method for manufacturing a positive electrode for a lithium secondary battery according to the present invention.
Figure 3 is a drawing showing the results of measuring the wet adhesion of the insulating layers of examples and comparative examples.
Figure 4 is a graph showing the discharge capacity measured to evaluate the capacity development of the battery cells of Examples 4 to 6 (room temperature discharge characteristics).
Figure 5 is a graph showing the discharge capacity measured to evaluate the capacity development of the battery cells of Examples 4 to 6 (high-temperature discharge characteristics).

The present invention is susceptible to various modifications and various embodiments, and specific embodiments will be described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

In the present invention, it should be understood that terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

In addition, in the present invention, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only the case where it is "directly below" the other part, but also the case where there is another part in between. Furthermore, in the present application, being disposed "on" may include the case where it is disposed below as well as above.

In the present invention, the “insulating layer” means an insulating member formed by applying and drying from at least a portion of the non-conductive portion of the electrode current collector to at least a portion of the electrode active material layer.

In the present invention, "wet adhesion" means the adhesion of an insulating layer measured while immersed in an electrolyte. More specifically, the wet adhesion can be measured by immersing a metal specimen on which an insulating layer is formed in an electrolyte, applying ultrasonic waves, and then checking whether the insulating layer swells or detaches.

In the present invention, the term "metal specimen" refers to a space where an insulating layer is formed, and may mean a metal collector used in the manufacture of an electrode, and may be a metal collector punched to have a predetermined width and a predetermined length. For example, the metal specimen may be aluminum, copper, or an aluminum alloy.

In the present invention, the term "overlay region" may mean a region in an electrode where an insulating layer is formed. More specifically, the insulating layer covers from at least a part of a non-conductive region in an electrode where an active material layer is formed to at least a part of the active material layer, and the region in which the insulating layer is formed in the active material layer may be referred to as an overlay region.

Hereinafter, the present invention will be described in more detail.

Cathode for lithium secondary battery

In one embodiment, the present invention comprises: a current collector; an active material layer formed on one or both sides of the current collector, the active material layer including a positive electrode active material, a conductive material, and a non-aqueous binder; and an insulating layer positioned on a side of the active material layer.

In addition, the insulating layer is formed with an aqueous binder substituted with a non-aqueous solvent. In the present invention, by applying an aqueous binder when forming the insulating layer, wet adhesiveness is increased, and the insulating layer can be stably applied to an anode vulnerable to moisture through substitution of a non-aqueous solvent.

The electrode for a secondary battery according to the present invention has an advantage in that it can suppress capacity expression, etc. by preventing the movement of lithium ions in the overlay region of the electrode by including an insulating layer having excellent wet adhesion.

In general, the positive electrode in a secondary battery exists in a state impregnated with an electrolyte, but the conventional insulating layer has a problem in that the wet adhesive strength in a state impregnated with an electrolyte is reduced, so that the movement of lithium ions in the overlay region of the positive electrode is not prevented, resulting in the development of capacity. In particular, lithium ions may precipitate when the capacity is developed in the overlay region of the positive electrode, which may result in a decrease in the stability of the battery cell. In the present invention, when manufacturing the positive electrode of a secondary battery, an insulating layer is formed using an aqueous binder substituted with a non-aqueous solvent identical to the solvent of the positive electrode slurry, thereby suppressing gelation due to a difference in the type of binder between the active material layer and the coating layer. In particular, the insulating layer is dried simultaneously with the solvent of the positive electrode slurry in the drying step, so that cracks between the active material layer and the insulating layer due to a drying speed or temperature difference can be prevented.

In addition, the insulating layer further contains inorganic particles, thereby enhancing electrical insulation and thermal safety and suppressing thermal expansion.

Meanwhile, the wet adhesion of the insulating layer can be measured by immersing the metal specimen on which the insulating layer has been formed in an electrolyte, applying ultrasonic waves, and then checking whether the insulating layer formed on the metal specimen is swelling or detaching.

The electrolyte used in the above wet adhesion measurement may include an organic solvent and an electrolyte salt, and the electrolyte salt may be a lithium salt. The lithium salt may be any of those commonly used in non-aqueous electrolytes for lithium secondary batteries without limitation. For example, the anions of the lithium salts above include F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , PF ₆ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , CF ₃ (CF ₂ ) It may include one or two or more selected from the group consisting of ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

As the organic solvent included in the above-mentioned electrolyte, those commonly used in electrolytes for lithium secondary batteries can be used without limitation, and for example, ethers, esters, amides, linear carbonates, or cyclic carbonates can be used alone or in combination of two or more. Among these, a representative example can include a carbonate compound that is a cyclic carbonate, a linear carbonate, or a mixture thereof.

In the positive electrode for a lithium secondary battery according to the present invention, the insulating layer may include an aqueous binder.

In a specific example, the aqueous binder may be at least one selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluoroelastomer, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose. In a specific example, the aqueous binder may be at least one selected from the group consisting of styrene-butadiene rubber, acrylate styrene-butadiene rubber, acrylonitrile-butadiene rubber, and acrylonitrile-butadiene-styrene rubber. For example, the aqueous binder may be styrene-butadiene rubber.

In the past, polyvinylidene fluoride (hereinafter, PVDF) was used as an insulating layer binder for the positive electrode, but this had a problem in that wet adhesive strength was reduced when impregnated with an electrolyte. Therefore, in the present invention, styrene-butadiene rubber can be used as the binder polymer. Meanwhile, when styrene-butadiene rubber is used as the polymer binder, water can be used as a solvent, but in this case, when the insulating composition is applied for simultaneous coating with the positive electrode slurry, gelation may occur between the insulating composition and the positive electrode slurry due to a difference in the type of binder.

In a specific example, the aqueous binder may be an aqueous binder substituted with a non-aqueous organic solvent. Here, the non-aqueous organic solvent may be at least one selected from the group consisting of N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), gamma butyrolactone, methyl alcohol, ethyl alcohol, and isopropyl alcohol.

For example, the aqueous binder may be a styrene-butadiene rubber substituted with an NMP solvent. More specifically, an insulating layer may be formed by applying an insulating composition so as to cover at least a portion of the non-woven portion to at least a portion of the active material layer and then drying the composition at a temperature of about 50 to 300° C. At this time, the solvent may be removed during the drying process, so that the insulating layer may exist as a styrene-butadiene rubber substituted with the NMP, instead of the styrene-butadiene rubber dispersed in the solvent.

In addition, the insulating layer can improve the safety of the battery by including inorganic particles, and can also improve the strength of the insulating layer. The amount of the inorganic particles can be appropriately adjusted in consideration of the viscosity, thermal resistance, insulation, filling effect, dispersibility, or stability of the insulating composition. In general, as the size of the inorganic particles increases, the viscosity of the composition containing them increases, and the possibility of sedimentation in the insulating composition increases. In addition, as the size decreases, the thermal resistance tends to increase. Therefore, in consideration of the above points, an appropriate type and size of inorganic particles can be selected, and if necessary, two or more types of inorganic particles can be used together.

In a specific example, the inorganic particles of the insulating layer may be at least one selected from the group consisting of AlOOH, Al ₂ O ₃ , γ-AlOOH, Al(OH) ₃ , Mg(OH) ₂ , Ti(OH) ₄ , MgO, _CaO , Cr ₂ O ₃ , _{MnO 2} , Fe ₂ O ₃ , Co 3 O ₄ , NiO, ZrO ₂ , BaTiO ₃ , SnO ₂ , CeO 2 , Y ₂ O ₃ , SiO ₂ , silicon carbide (SIC) and boron nitride (BN), and may be at least one selected from the group consisting of AlOOH, Al ₂ O ₃ , γ-AlOOH and Al(OH) ₃ . For example, the inorganic particles may be AlOOH.

The weight ratio of the inorganic particles and the aqueous binder may be in the range of 1:99 to 95:5, or 10:90 to 70:30; 20:80 to 60:40, or 40:60 to 60:40. For example, the weight ratio of the inorganic particles and the aqueous binder in the insulating composition may be 50:50. Meanwhile, when the content of the aqueous binder is too small, it may be difficult to exhibit the insulating effect intended in the present invention, and the adhesive strength with the electrode may be weakened. In addition, when the content of the aqueous binder is too large, the insulating composition may flow down in the overlay area during coating of the electrode, which may cause a decrease in the safety of the battery cell.

The average particle size of the above inorganic particles may be 0.1 ㎛ to 100 ㎛, 0.5 ㎛ to 80 ㎛, 1 ㎛ to 50 ㎛; 2 ㎛ to 30 ㎛; 3 ㎛ to 20 ㎛ or 5 ㎛ to 10 ㎛. When the size of the above inorganic particles is within the above range, they can be uniformly coated on the electrode and the resistance of lithium ions can be minimized to secure the performance of the lithium secondary battery.

In another example, the insulating composition may include first and second inorganic particles having different particle diameters, but may have a bimodal particle size distribution. This means that the inorganic particles are a mixture of small particles and large particles, and the empty spaces between the first inorganic particles of the large particles can be filled by the second inorganic particles of the small particles, and dispersion of an appropriate amount of inorganic particles can be possible. However, this is not limited thereto.

Meanwhile, the thickness of the insulating layer may be determined in a range of 0.2 ㎛ to 100 ㎛, specifically, 1 ㎛ to 50 ㎛, and more specifically, 1 ㎛ to 30 ㎛; 2 ㎛ to 30 ㎛; 3 ㎛ to 20 ㎛; or 5 ㎛ to 15 ㎛. If the thickness of the coating portion is too thin, it may be difficult to expect an effect for improving safety due to the application of the insulating layer.

In addition, the active material layer may include a cathode active material. In a specific example, the cathode active material may include any cathode active material that is commonly used, and may include, but is not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide that combines these.

In addition, the content of the positive electrode active material may be 85 to 95 parts by weight with respect to 100 parts by weight of the active material layer, and specifically, may be 88 to 95 parts by weight, 90 to 95 parts by weight, 86 to 90 parts by weight, or 92 to 95 parts by weight.

At this time, the conductive material can be used to improve the performance of the anode, such as electrical conductivity, and at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber can be used. For example, the conductive material can include acetylene black.

In addition, the conductive agent may be included in an amount of 1 to 10 parts by weight, specifically 2 to 8 parts by weight; or 2 to 6 parts by weight, based on 100 parts by weight of the active material layer.

In addition, the binder may include at least one resin selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, and copolymers thereof. As an example, the binder may include polyvinylidene fluoride.

In addition, the binder may be included in an amount of 1 to 10 parts by weight, specifically 2 to 8 parts by weight; or 2 to 6 parts by weight, based on 100 parts by weight of the total active material layer.

In addition, the average thickness of the active material layer is not particularly limited, but may be specifically 0.1 ㎛ to 20 ㎛, and more specifically 0.1 ㎛ to 15 ㎛; 0.1 ㎛ to 10 ㎛; 2 ㎛ to 10 ㎛; 4 ㎛ to 10 ㎛; or 5 ㎛ to 9 ㎛.

Meanwhile, the positive electrode for a lithium secondary battery according to the present invention can use a current collector that has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. can be used, and in the case of aluminum or stainless steel, a surface-treated one with carbon, nickel, titanium, silver, etc. can be used. In addition, the current collector can form fine unevenness on the surface to increase the adhesive strength of the positive electrode active material, and can be in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. In addition, the average thickness of the current collector can be appropriately applied in the range of 3 to 500 ㎛ in consideration of the conductivity and total thickness of the positive electrode to be manufactured.

Method for manufacturing a cathode for lithium secondary battery

In one embodiment, the present invention includes a step of applying a positive electrode slurry including a positive electrode active material, a conductive material, and a non-aqueous binder to one side or both sides of a current collector; a step of applying an insulating composition including an aqueous binder substituted with a non-aqueous solvent so as to cover a portion of the positive electrode slurry applied to the current collector from at least a portion of a non-conductive portion of the current collector; and a step of drying the positive electrode slurry and the insulating composition applied to the current collector. In addition, the positive electrode slurry and the insulating composition include the same non-aqueous solvent.

FIG. 2 is a flow chart of a method for manufacturing a positive electrode for a lithium secondary battery according to the present invention. Referring to FIG. 2, the method for manufacturing a positive electrode for a lithium secondary battery according to the present invention may include applying a positive electrode slurry to one side or both sides of a current collector, and applying an insulating composition to cover a portion of the positive electrode slurry applied to the current collector from at least a portion of a non-coated portion of the current collector. Meanwhile, the insulating composition may be applied to the positive electrode slurry while it is not dried. Here, the term “not dried” may mean a slurry that has not undergone a separate drying process in a drying device or equipment. In addition, the present invention may include a step of drying the positive electrode slurry and the insulating composition applied to the current collector. In particular, according to the method for manufacturing a positive electrode for a lithium secondary battery according to the present invention, the positive electrode slurry and the insulating composition applied to the current collector are dried at the same time to increase the adhesive strength between the positive electrode active material and the insulating layer, thereby reducing the interfacial resistance and forming a dense insulating layer that improves mechanical property problems such as breakage. In addition, the efficiency of the bipolar manufacturing process can be increased.

Meanwhile, in the method for manufacturing a positive electrode for a lithium secondary battery according to the present invention, the positive electrode slurry and the insulating composition are characterized in that they contain the same non-aqueous organic solvent. When the positive electrode slurry and the insulating composition use the same solvent, problems such as gelation problems of different binders or cracking during drying due to differences in boiling points can be solved.

The above non-aqueous organic solvent may be at least one selected from the group consisting of N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), gamma butyrolactone, methyl alcohol, ethyl alcohol, and isopropyl alcohol.

In a specific example, the non-aqueous organic solvent may be at least one selected from the group consisting of N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO), and may be at least one selected from the group consisting of N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc).

For example, the non-aqueous organic solvent may be an amide-based organic solvent, and the same solvent as that used in preparing the positive electrode slurry may be used, and the non-aqueous organic solvent may be N-methyl-pyrrolidone (NMP).

When the solvent of the above positive electrode slurry is NMP, the solvent of the insulating composition may be NMP, and in particular, by using NMP as the solvent of the insulating composition, cracks occurring at the boundary between the insulating coating portion and the active material layer in the overlay region of the electrode can be prevented. The insulating composition for the electrode of the secondary battery according to the present invention can be coated and dried simultaneously with the positive electrode slurry. In particular, in the drying process, NMP can be used as a substitution solvent.

The method for manufacturing a positive electrode for a lithium secondary battery according to the present invention is described in detail as follows.

Step of applying anode slurry to one or both sides of the entire body (S10)

A method for manufacturing a positive electrode for a lithium secondary battery according to the present invention includes a step of applying positive electrode slurry to one or both sides of a current collector.

At this time, the current collector can be a cathode for a lithium secondary battery according to the present invention that has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. can be used, and in the case of aluminum or stainless steel, a surface-treated one with carbon, nickel, titanium, silver, etc. can also be used. For example, the current collector can be aluminum.

In addition, in the slurry for the positive electrode active material, all positive electrode active materials commonly used in positive electrodes can be used, and lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a lithium composite oxide combining these can be used, but are not limited thereto.

The non-aqueous binder included in the slurry for the above positive electrode active material may include at least one resin selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, and copolymers thereof. As an example, the binder may include polyvinylidene fluoride.

At this time, the conductive material can be used to improve the performance of the anode, such as electrical conductivity, and at least one selected from the group consisting of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber can be used. For example, the conductive material can include acetylene black.

Furthermore, the solvent used in the cathode slurry may be a non-aqueous organic solvent, and may be at least one selected from the group consisting of N-methyl-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), ethylene carbonate (EC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate (BC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), acetonitrile, dimethoxyethane, tetrahydrofuran (THF), gamma butyrolactone, methyl alcohol, ethyl alcohol, and isopropyl alcohol, for example, It could be N-methyl-2-pyrrolidone (NMP).

Step (S20) of applying an insulating composition to cover a portion of the cathode slurry applied to the entire collector from at least a portion of the entire collector's non-conductive portion.

The method for manufacturing a positive electrode for a lithium secondary battery according to the present invention can apply an insulating composition including inorganic particles and an aqueous binder to cover a portion of a positive electrode slurry applied to a current collector from at least a portion of a non-conductive portion of the current collector.

At this time, the anode slurry may be in an undried state. Here, undried may mean a slurry that has not undergone a separate drying process in a drying device or equipment.

At this time, the insulating composition can provide excellent wet adhesion by including inorganic particles and an aqueous binder. Accordingly, the movement of lithium ions in the overlay region of the positive electrode can be suppressed, and lithium ions can be prevented from being precipitated.

Lithium secondary battery

In addition, the present invention, in one embodiment,

A lithium secondary battery including a positive electrode for a lithium secondary battery according to the present invention described above is provided.

A lithium secondary battery according to the present invention may include the cathode, anode, and a separator positioned between the cathode and anode of the present invention as described above.

In particular, the lithium secondary battery according to the present invention has an advantage in that the insulating layer has excellent wet adhesion in an electrolyte, thereby preventing the movement of lithium ions in the overlay region of the electrode, thereby suppressing capacity expression, etc. Accordingly, the lithium secondary battery according to the present invention can improve stability.

Here, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector and containing a negative electrode active material. Specifically, the negative electrode is manufactured by applying, drying, and pressing a negative electrode active material on the negative electrode current collector, and, if necessary, a conductive material, an organic binder polymer, a filler, etc. as described above may be further optionally included.

In addition, the negative electrode active material has a complete layered crystal structure, such as natural graphite.

Soft carbon having a fully formed graphite, a low-crystalline layered crystal structure (graphene structure; a structure in which hexagonal honeycomb-shaped planes of carbon are arranged in layers), and such structures

Carbon and graphite materials such as hard carbon, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotubes, fullerene, and activated carbon, which are mixed with amorphous parts; metal composite oxides such as Li _x Fe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _1-x Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me', Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, and halogens; 0<x≤1;1≤y≤3;1≤z≤8); lithium metal; lithium alloys; silicon-based alloys; tin-based alloys; Metal oxides such as SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ and Bi ₂ O ₅ ; conductive polymers such as polyacetylene; Li-Co-Ni materials; titanium oxide; lithium titanium oxide, etc. can be used.

As an example, the negative electrode active material may include graphite and silicon (Si)-containing particles together, and the graphite may include at least one of natural graphite having a layered crystal structure and artificial graphite having an isotropic structure, and the silicon (Si)-containing particles may include particles containing silicon (Si) as a main component as a metal component, and may include silicon (Si) particles, silicon oxide (SiO ₂ ) particles, or a mixture of the silicon (Si) particles and silicon oxide (SiO 2 ) particles.

In this case, the negative electrode active material may include 80 to 95 parts by weight of graphite and 1 to 20 parts by weight of silicon (Si)-containing particles based on 100 parts by weight of the total. The present invention can reduce lithium consumption and irreversible capacity loss during initial charge and discharge of a battery while improving the charge capacity per unit mass by controlling the contents of graphite and silicon (Si)-containing particles included in the negative electrode active material within the above range.

In addition, the negative active material layer may have an average thickness of 100 ㎛ to 200 ㎛, and specifically, may have an average thickness of 100 ㎛ to 180 ㎛; 100 ㎛ to 150 ㎛; 120 ㎛ to 200 ㎛; 140 ㎛ to 200 ㎛ or 140 ㎛ to 160 ㎛.

In addition, the negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, nickel, titanium, calcined carbon, etc. can be used. In the case of copper or stainless steel, a material surface-treated with carbon, nickel, titanium, silver, etc. can also be used.

In addition, the negative current collector, like the positive current collector, can form fine unevenness on the surface to strengthen the bonding strength with the negative active material, and can be in various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. In addition, the average thickness of the negative current collector can be appropriately applied in the range of 3 to 500 ㎛ in consideration of the conductivity and total thickness of the negative electrode to be manufactured.

In addition, the separator is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The separator is not particularly limited as long as it is commonly used in the art, but specifically, a sheet or nonwoven fabric made of chemically resistant and hydrophobic polypropylene; glass fiber; or polyethylene, etc. may be used, and in some cases, a composite separator in which inorganic particles/organic particles are coated with an organic binder polymer on a porous polymer substrate such as the sheet or nonwoven fabric may be used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also function as the separator. In addition, the pore diameter of the separator may be 0.01 to 10 ㎛ on average, and the thickness may be 5 to 300 ㎛ on average.

Meanwhile, the positive and negative electrodes may be wound in a jelly roll shape and stored in a cylindrical battery, a square battery, or a pouch-shaped battery, or stored in a pouch-shaped battery in a folding or stack-and-folding form, but are not limited thereto.

In addition, the lithium salt-containing electrolyte according to the present invention may be composed of an electrolyte and a lithium salt, and a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, etc. may be used as the electrolyte.

As the above non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxy ethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolan, formamide, dimethylformamide, dioxolan, acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxy methane, dioxolan derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrropionate, and ethyl propionate can be used. there is.

As the organic solid electrolyte, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyagitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, polymerizers containing ionic dissociation groups, and the like can be used.

As the above-mentioned inorganic solid electrolyte, for example, Li nitrides, halides, sulfates, etc., such as Li ₃ N, LiI, Li ₅ Ni ₂ , Li ₃ N _- LiI-LiOH, LiSiO ₄ , LiSiO _{4 -LiI} -LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Li 4 SiO 4 -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , etc. can be used.

The above lithium salt is a substance that is easily dissolved in a non-aqueous electrolyte, and for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB10Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, lithium chloroborane, lithium lower aliphatic carboxylic acid, lithium 4-phenylboronic acid, imide, etc. can be used.

In addition, for the purpose of improving the charge/discharge characteristics, flame retardancy, etc., the electrolyte may contain, for example, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoromethane may be further contained to provide incombustibility, carbon dioxide gas may be further contained to improve high-temperature storage characteristics, and FEC (Fluoro-Ethylene Carbonate), PRS (Propene sultone), etc. may be further contained.

Meanwhile, in one embodiment, the present invention provides a battery module including the secondary battery described above as a unit battery, and a battery pack including the battery module.

The above-mentioned battery pack can be used as a power source for medium-to-large-sized devices that require high-temperature stability, long cycle characteristics, and high-rate characteristics, and specific examples of such medium-to-large-sized devices include: a power tool that is powered by an electric motor and moves; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system, and more specifically, a hybrid electric vehicle (HEV) can be mentioned, but is not limited thereto.

Furthermore, the positive and negative electrodes may be wound in a jelly roll shape and stored in a cylindrical battery, a square battery, or a pouch-shaped battery, or may be stored in a pouch shape in a folding or stack-and-folding form. For example, the lithium secondary battery according to the present invention may be a pouch-shaped battery.

As described above, the lithium secondary battery including the cathode active material according to the present invention can be used in a battery module or battery pack including a plurality of unit cells. Specifically, it is useful in portable devices such as mobile phones, notebook computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

Hereinafter, the present invention will be described in more detail through examples and experimental examples.

However, the following examples and experimental examples are only intended to illustrate the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

Example 1.

For 100 g of a styrene-butadiene rubber (hereinafter, SBR, ZEON BM451B product) binder dispersed in water as a solvent at a ratio of 60:40 (parts by weight), 500 g of N-methyl-2-pyrrolidone (NMP) solvent was added and stirred. Then, the stirred mixture was heated at 100 to 120°C for 2 hours to completely evaporate the contained water, thereby preparing an NMP-substituted SBR binder. Then, the NMP-substituted SBR binder and inorganic particles were mixed and stirred at a weight ratio of 50:50 to prepare an insulating composition. The viscosity of the prepared insulating composition is 5,000 cP.

Examples 2 to 4, Comparative Examples 1 to 2.

An insulating coating solution was obtained in the same manner as in Example 1, except that the content of inorganic particles and binder was changed when preparing the insulating composition.

The specific compositions of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1 below.

division Insulating composition menstruum Weapon particles bookbinder Weapon Particle:Binder (Weight Ratio) Example 1 NMP AlOOH SBR 50:50 Example 2 NMP AlOOH SBR 60:40 Example 3 NMP AlOOH SBR 75:25 Example 4 NMP AlOOH SBR 80:20 Comparative Example 1 NMP AlOOH PVDF 80:20 Comparative Example 2 NMP AlOOH PVDF 88:12

Experimental Example 1. Measurement of wet adhesion of insulation layer

In order to evaluate the adhesive strength of the insulating layer according to the present invention, the following experiment was conducted.

Metal specimen with formed insulating layer

The insulating compositions manufactured in Examples 1-4 and Comparative Examples 1 and 2 were coated on aluminum metal foil and dried to prepare a metal specimen having an insulating layer of about 10 ㎛ in thickness. The metal specimen having the insulating layer formed thereon was punched into a size of 2 cm × 2 cm using a puncher for measuring adhesion.

Ultrasonic authentication

200 g of electrolyte EC/EMC=3/7(vol.%) was added to a 250 ml beaker, and a metal specimen having an insulating layer formed thereon was immersed in the electrolyte. In order to control the movement of the metal specimen, the metal specimen was fixed with a jig.

Then, ultrasonic waves were applied to the electrolyte solution in which the metal specimen was impregnated using an ultrasonic disperser (BANDELIN, 4200). At this time, the ultrasonic wave application conditions were as follows.

- Frequency: 20kHz

- Tip diameter: 13 mm (TS-113)

- Amplitude: 100%

(When using 13 mm tip, peak-to-peak 132 ㎛)

And, the results are shown in Table 2 and Figure 2 below.

division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 furtherance AlOOH:SBR
=50:50 AlOOH:SBR
=60:40 AlOOH:SBR
=75:25 AlOOH:SBR
=80:20 AlOOH:PVDF
=80:20 AlOOH:PVDF
=88:12 Time (minutes) 19 19 19 15 5 10 End temperature (℃) 109 109 109 100 71 87 Wet Adhesion Comparison No swelling and no tearing No swelling and no tali No swelling and no tali No swelling and no tali Swelling occurs Swelling and tearing occur

Figure 2 is a drawing showing the results of measuring the wet adhesion of the insulating layers of Examples 1 and 4 and Comparative Example 1-2.

Looking at Table 2 and Figure 2, the electrode specimen of Example 1 did not experience swelling or detachment in the insulating layer. However, in the case of Example 1, the boiling point of EMC was 107.5℃ due to the increase in temperature of the electrolyte caused by the application of ultrasonic waves, and the measurement environment changed due to the evaporation of the solvent, so the measurement was stopped when it reached 109℃.

In addition, for Examples 2 and 3, although not shown in the photographs, no swelling or detachment occurred in the insulating layer of the electrode specimen, as in Example 1. However, since the boiling point of EMC was 107.5°C, the measurement environment changed as the solvent evaporated, and the measurement was stopped when it reached 109°C.

In the case of Example 4, when ultrasonic waves were applied to the electrolyte, no swelling or detachment occurred in the electrode specimen for 15 minutes. However, although not disclosed in the drawing, when the temperature of the electrolyte reached 108°C due to the continued application of ultrasonic waves, swelling and detachment of the electrode specimen occurred.

In addition, in the case of Comparative Examples 1 and 2, swelling and detachment occurred in the electrode specimen within 5 minutes of applying ultrasonic waves to the electrolyte.

Through this, it was confirmed that the insulating layer of the example had superior wet adhesion compared to the insulating layer of Comparative Example 1-2.

Experimental Example 2. Evaluation of Capacity Development of Battery Cells

In order to evaluate the performance of the positive electrode including the insulating layer according to the present invention, half cells were manufactured and then the capacity development was evaluated.

Manufacturing of Half Cells

As a positive electrode active material, 96 parts by weight of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , 2 parts by weight of PVdF as a binder, and 2 parts by weight of carbon black as a conductive material were weighed and mixed in an N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry. The slurry for the active material layer was applied to aluminum foil, dried, and then rolled to prepare a positive electrode having a positive electrode active material layer (average thickness: 130 μm).

Then, the insulating coating solution obtained in Examples 1 to 3 was dip-coated on the positive electrode and dried in a convection oven (130°C) to form an insulating layer with a thickness of 10 μm on the positive electrode. Lithium foil was used as the negative electrode, and coin-type half-cells were manufactured using an electrolyte containing 1 M LiPF ₆ in a solvent of EC:DMC:DEC = 1:2:1.

Insulating layer battery Example 1 Example 5 Example 2 Example 6 Example 3 Example 7

Discharge capacity measurement

For the batteries of Examples 5 to 7, the discharge characteristics were evaluated under the following conditions. And, the discharge characteristics were measured at room temperature (25°C) and high temperature (45°C), respectively.

- Discharge: 0.1C, 0.33C, 0.5C, 1.0C, 2.5, cut-off

Meanwhile, in order to compare whether each battery exhibited capacity, a battery cell including an electrode without an insulating layer formed was used as Comparative Example 3. The results are shown in Table 4 and Fig. 3, Table 5 and Fig. 4.

division Insulating composition Room temperature discharge rate (%) menstruum Weapon particles bookbinder Weapon Particle: Binder
(Weight ratio) 0.1C 0.33C 0.5C 1.0C Comparative Example 3 - - - - 100.00 100.00 100.00 100.00 Example 5 NMP AlOOH SBR 50:50 0.33 0.06 0.05 0.00 Example 6 NMP AlOOH SBR 60:40 0.60 0.09 0.05 0.03 Example 7 NMP AlOOH SBR 75:25 0.27 0.06 0.03 0.00

division Insulating composition High temperature discharge rate (%) menstruum Weapon particles bookbinder Weapon Particle: Binder
(Weight ratio) 0.1C 0.33C 0.5C 1.0C Comparative Example 3 - - - - 100.00 100.00 100.00 100.00 Example 5 NMP AlOOH SBR 50:50 2.23 0.21 0.15 0.05 Example 6 NMP AlOOH SBR 60:40 1.41 0.18 0.15 0.03 Example 7 NMP AlOOH SBR 75:25 15.35 0.18 0.15 0.03

Referring to Tables 4 and 5 above and Figures 3 and 4, in the case of Example 7, it was confirmed that some of the capacity was developed at 0.1C discharge at high temperature discharge (45°C), but in the batteries of Examples 5 and 6, almost no capacity was developed at room temperature discharge (25°C).

These results indicate that the insulating layer has excellent wet adhesion in the electrolyte, thereby preventing the movement of lithium ions in the overlay region of the electrode, thereby suppressing capacity development, etc. during discharge. Accordingly, the lithium secondary battery according to the present invention appears to be able to improve safety, etc. while suppressing capacity degradation due to an increase in cycles.

Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes may be made to the present invention without departing from the spirit and technical scope of the present invention as set forth in the claims below.

Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the scope of the patent claims.

Claims (11)

The whole house;
An active material layer formed on one or both sides of the entire body, comprising a positive electrode active material, a conductive material, and a non-aqueous binder; and
Including an insulating layer located on the side of the above active material layer,
The above insulating layer is positioned on the current collector, and is structured to cover a part of the active material layer applied to the current collector from a part of the non-conductive part of the current collector.
The above insulating layer is a positive electrode for a lithium secondary battery including an aqueous binder.
In paragraph 1,
The above insulating layer is positioned on the current collector, and is structured to cover a part of the sliding area of the active material layer applied to the current collector from a part of the non-conductive portion of the current collector.
A positive electrode for a lithium secondary battery, wherein the height of the insulating layer is in the range of 10 to 50% of the height of the active material layer.
In paragraph 1,
The above insulating layer is positioned on the current collector, and is structured to cover a part of the sliding area of the active material layer applied to the current collector from a part of the non-conductive portion of the current collector.
A positive electrode for a lithium secondary battery, wherein the height of the insulating layer is in the range of 50 to 100% of the height of the active material layer.
In paragraph 1,
A positive electrode for a lithium secondary battery, the thickness of the insulating layer being in the range of 1㎛ to 50㎛ on average.
In paragraph 1,
The above insulating layer is,
Further comprising inorganic particles dispersed within an aqueous binder substituted with a non-aqueous solvent,
A positive electrode for a lithium secondary battery, characterized in that the weight ratio of inorganic particles and aqueous binder is in the range of 1:99 to 95:5.
In paragraph 5,
A positive electrode for a lithium secondary battery, wherein the inorganic particles are at least one _{selected from the} group consisting of AlOOH, Al ₂ O ₃ , γ-AlOOH, Al(OH) ₃ , Mg(OH) ₂ , Ti(OH _{) 4} , MgO, CaO, _{Cr 2} O ₃ , MnO ₂ , Fe 2 O ₃ , Co 3 O ₄ , NiO, ZrO ₂ , BaTiO ₃ , SnO 2 , CeO 2 , Y ₂ O ₃ , SiO ₂ , silicon carbide (SIC) and boron nitride (BN).
In paragraph 1,
A lithium secondary battery cathode, wherein the aqueous binder is at least one selected from the group consisting of styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluoroelastomer, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose.
In paragraph 1,
A positive electrode for a lithium secondary battery, wherein the non-aqueous binder is at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropene (PVDF-co-HFP, Poly(vinylidene fluoride-co-hexafluoropropene)), poly(ethylene oxide) (PEO, Poly(ethylene oxide)), polyacrylic acid (PAA), polyimide (PI), polyamideimide (PAI), and polyimide-polyamideimide copolymer (PI-PAI).
In paragraph 1,
The non-aqueous binder is polyvinylidene fluoride (PVDF).
A positive electrode for a lithium secondary battery, characterized in that the aqueous binder is a styrene-butadiene rubber substituted with N-methyl-2-pyrrolidone.
A lithium secondary battery comprising a positive electrode for a lithium secondary battery according to any one of claims 1 to 9. delete

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