Electrode mixture composition, method for manufacturing dry electrode using same, and secondary battery comprising dry electrode manufactured therefrom

Abstract

The present specification discloses technology related to an electrode mixture composition. The electrode mixture composition comprises: a binder mixture including a large-crystalline binder having a crystal size of 50 nm or more and a small-crystalline binder having a crystal size of less than 50 nm; and an electrode active material. By utilizing a binder mixture in which binders having different crystal sizes are mixed and using different degrees of fiberization, the electrode mixture composition can improve the mechanical properties of a powder sheeting film and improve the processability of a calendaring process, and thereby provide a secondary battery having excellent resistance characteristics.

Description

Electrode composite composition, method for producing a dry electrode using the same, and secondary battery including a dry electrode produced therefrom

[0001] The present specification relates to an electrode composite composition, a method for manufacturing a dry electrode using the same, and a secondary battery including a dry electrode manufactured therefrom.

[0002]

[0003] Secondary batteries are used not only in small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in large products requiring high output such as electric vehicles and hybrid vehicles, as well as in power storage devices that store surplus generated power or renewable energy and power storage devices for backup purposes.

[0004] Typically, secondary batteries are manufactured by applying electrode active material slurry to a positive electrode current collector and a negative electrode current collector to form an electrode active material layer, then manufacturing a positive electrode and a negative electrode through a drying and rolling process, and then laminating these on both sides of a separator to form an electrode assembly of a predetermined shape, and then housing the electrode assembly in a battery case, injecting electrolyte, and sealing the electrode assembly.

[0005] Meanwhile, during the drying process of the electrode active material slurry, the solvent contained in the slurry may evaporate, causing defects such as pinholes or cracks in the electrode active material layer formed on the current collector. In addition, since the inside and outside of the electrode active material slurry are not uniformly dried during the drying process, there is a concern that the powder floating phenomenon due to the difference in solvent evaporation rate may occur, i.e., the powder in the area that dries first may rise and form a gap with the area that dries relatively later, which may deteriorate the electrode quality.

[0006] To solve the above problem, a drying device capable of controlling the evaporation rate of the solvent so that the inside and outside of the electrode active material slurry can be dried evenly is being considered, but such drying devices are very expensive and require considerable cost and time to operate, which is disadvantageous in terms of manufacturing process.

[0007] On the other hand, the solvent typically used in electrode active material slurries is N-methyl-2-pyrrolidone (NMP). Its high boiling point necessitates high heat energy and a very long drying process for drying, making it highly unsuitable for mass production. Furthermore, NMP is toxic and harmful to living organisms, making it unfriendly to the environment.

[0008] Accordingly, there has been a recent trend of active research on dry electrodes that manufacture electrodes without using solvents. The dry electrode is generally manufactured by laminating a free-standing electrode composite film manufactured in the form of a sheet containing an electrode active material, a binder, a conductive material, etc., onto a current collector. This electrode composite film includes a process of first mixing an electrode active material, a carbon material as a conductive material, and a fiberizable binder together using a blender, etc., and then applying a shear force through a process such as jet milling or kneading to fiberize the binder, and then calendering the obtained mixture into a film form to manufacture a free-standing film.

[0009] Dry electrode films require precise control of mixing, kneading, and calendering conditions to ensure uniform dispersion and fiberization of the binder within the active material to ensure optimal appearance and mechanical properties. However, optimized process conditions, such as kneading time, vary depending on the binder type. This significantly impacts the film's mechanical properties, making it difficult to guarantee electrode properties.

[0010] Accordingly, research and development are needed to optimize process conditions according to the type of binder and to determine which binder is effective in improving the appearance and mechanical properties of the film.

[0011]

[0012] In one aspect of the present specification, it is an object to provide an electrode composite composition capable of improving the mechanical properties of a powder sheeting film by utilizing different degrees of fiberization by applying a binder mixture in which binders having different crystal sizes are mixed.

[0013] In addition, in another aspect of the present specification, it is intended to provide a method for manufacturing a dry electrode that can dramatically improve the processability of a calendaring process by improving the mechanical properties of a powder sheeting film by inducing the coexistence of hard and soft portions of a binder matrix in a powder sheeting film with appropriate uniformity by utilizing the fact that binders with different crystal sizes have different degrees of fiberization.

[0014] In addition, in another aspect of the present specification, by applying a dry electrode having excellent appearance characteristics and excellent mechanical properties, manufactured by the method for manufacturing the dry electrode, it is intended to provide a secondary battery having excellent durability, excellent electrolyte wettability due to the presence of both hard and soft portions in the binder matrix within the electrode, excellent lithium ion mobility, and improved resistance characteristics.

[0015]

[0016] [1] In one aspect of the present specification, an electrode composite composition is provided, characterized by including a binder mixture including a large-crystal binder having a crystal size of 50 nm or more and a small-crystal binder having a crystal size of less than 50 nm; and an electrode active material.

[0017] [2] In the above [1], an electrode composite composition can be provided in which the weight fraction of the large-crystal binder in the binder mixture is smaller than the weight fraction of the small-crystal binder.

[0018] [3] In the above [1] and / or [2], an electrode composite composition can be provided in which the large-crystal binder has a crystal size of 50 nm to 100 nm, and the small-crystal binder has a crystal size of 10 nm to 49 nm.

[0019] [4] In at least one of the above [1] to [3], an electrode composite composition can be provided that includes 5 to 45 parts by weight of a large-crystal binder and 55 to 95 parts by weight of a small-crystal binder, with respect to 100 parts by weight of the binder mixture.

[0020] [5] In at least one of the above [1] to [4], an electrode composite composition can be provided in which the binder mixture has R defined by the following formula 1 of 1.27 or less.

[0021] [Formula 1]

[0022] R = [C L x (1+W L )] / [(C S x (1+W S )]

[0023] In the above equation 1, C L and C S are the crystal sizes of the macrocrystal binder and the small-crystal binder, respectively, in nm, and W L and W S are the weight fractions of the large-crystal binder and the small-crystal binder, respectively, based on the total weight of the binder mixture.

[0024] [6] In at least one of the above [1] to [5], an electrode composite composition may be provided that includes a lithium transition metal compound containing at least one selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe).

[0025] [7] In at least one of the above [1] to [6], an electrode composite composition including polytetrafluoroethylene (PTFE) may be provided as the binder.

[0026]

[0027] [8] In another aspect of the present specification, a method for manufacturing a dry electrode is provided, characterized by comprising the steps of: (S1) preparing an electrode composite composition by mixing an electrode active material, a conductive material, and a binder mixture including a large-crystal binder having a crystal size of 50 nm or more and a small-crystal binder having a crystal size of less than 50 nm; (S2) kneading the electrode composite mixture while applying a shear force to obtain a mixed aggregate; (S3) pulverizing the mixed aggregate to obtain an electrode powder; and (S4) rolling the electrode powder to form a sheet to manufacture an electrode composite film.

[0028] [9] In the above [8], a method for manufacturing a dry electrode in which T defined by the following equation 2 is 5.7 min or less can be provided.

[0029] [Formula 2]

[0030] T = {[C L x (1+W L )] / [(C S x (1+W S )]} / t K

[0031] In the above equation 1, C L and C S are the crystal sizes of the macrocrystal binder and the small-crystal binder, respectively, in nm, and W L and W S are the weight fractions of the large-crystal binder and the small-crystal binder, respectively, based on the total weight of the binder mixture, and t K is a unitless number of minutes (min) for mixing time.

[0032]

[0010] In the above [8] and / or [9], the t K A method for manufacturing a dry electrode of 15 min to 25 min can be provided.

[0033]

[0011] In at least one of the above [8] to

[0010] , a method for manufacturing a dry electrode can be provided in which the roll temperature of the S4 step is 60°C to 150°C.

[0034]

[0012] In at least one of the above [8] to

[0011] , a method for manufacturing a dry electrode may be provided, including the step S4 of obtaining a powder-sheeting film by pre-sheeting the electrode powder (S4a); and the step S4 of manufacturing an electrode composite film by sheeting the powder-sheeting film two or more times (S4b).

[0035]

[0036]

[0013] In another aspect of the present specification, a secondary battery is provided including a dry electrode manufactured by at least one of the methods for manufacturing a dry electrode among [8] to

[0012] .

[0037]

[0038] The electrode composite composition according to the present specification can improve the mechanical properties of a powder sheeting film by utilizing different degrees of fiberization by applying a binder mixture in which binders having different crystal sizes are mixed.

[0039] In addition, the method for manufacturing a dry electrode according to the present specification can dramatically improve the fairness of the calendaring process by inducing the coexistence of hard and soft portions of the binder matrix in the powder sheeting film with appropriate uniformity by utilizing the fact that binders with different crystal sizes have different degrees of fiberization, thereby improving the mechanical properties of the powder sheeting film.

[0040] In addition, the secondary battery according to the present specification has excellent durability by applying a dry electrode having excellent appearance characteristics and excellent mechanical properties, manufactured by the method for manufacturing the dry electrode, and has excellent electrolyte wettability due to the presence of both hard and soft portions in the binder matrix within the electrode, thereby having excellent lithium ion mobility and improved resistance characteristics.

[0041]

[0042] Hereinafter, the present invention will be described in more detail.

[0043] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best possible manner.

[0044] In this specification, the term "mixture" means a mixture including an electrode active material and a binder (and in some cases, a conductive material), which is physically mixed to form a uniform dispersion phase, and may be a powder mixture as a product of the mixing process (mixing process) according to this specification, and may be substantially solvent-free. Here, substantially solvent-free means that no solvent is added or only a very small amount of solvent is added during mixing of the mixture.

[0045] In this specification, the “mixed aggregate” is a product of the kneading process (kneading process) according to this specification in which the above-mentioned composite mixture is subjected to shear force, the binder is fiberized, and the powder mixture is combined or linked to each other to convert into a paste-like aggregate, and may be a product of the kneading process (kneading process) according to this specification and has a solid content of 100%.

[0046] In this specification, “powder for electrode” may mean a material in a powder state in which the above mixed aggregate is pulverized to make the particle size smaller.

[0047] In this specification, the "electrode composite film" may mean a film manufactured in the form of a free-standing single sheet using an "electrode composite" including an electrode active material, a conductive material, and a binder without the involvement of a solvent. The term "free-standing" in this specification means that it can maintain its own shape without relying on other members and can be moved or handled on its own. The electrode composite film may be formed by compressing an electrode powder as described below. For example, the electrode powder may have a shape in which a layered structure is formed by being accumulated by compressing. The electrode powder is an electrode material in powder form including an electrode active material and a binder, and may be obtained, for example, by pulverizing an aggregate including an electrode active material and a binder as described below.

[0048] In this specification, the term "powder-sheeting film" refers to a film formed from the time when the electrode powder is first passed through a rolling roll in a roll-to-roll process to the time when it passes through the last rolling roll in the process, and may be a self-supporting sheet, but may have weak holding power. Here, the "powder-sheeting" refers to the process in which the electrode powder is manufactured into a self-supporting sheet by a rolling roll in a calendering process, and the "sheeting" refers to a calendering process performed in the process in which the powder-sheeted film is manufactured into an electrode composite film.

[0049] In the present specification, the electrode composite composition, the method for manufacturing a dry electrode, and the secondary battery each include at least one of the technical configurations described below, and may include any combination between technically possible configurations among the technical configurations below.

[0050]

[0051] Electrode composite composition

[0052] In one aspect, the electrode composite composition is characterized by including a binder mixture including a macrocrystalline binder having a crystal size of 50 nm or more and a small-crystalline binder having a crystal size of less than 50 nm; and an electrode active material.

[0053] The crystal size of the above binder can be measured using XRD analysis. Specifically, the XRD data obtained by X-ray diffraction analysis can be analyzed by the Rietveld refinement method. At this time, the X-ray diffraction analysis is performed using a Bruker D8 Endeavor (light source: Cu-Kα, λ=1.54Å, 40 kV, 40 mA) equipped with a LynxEye XE-T-position sensitive detector (4.1 slit). The sample is placed in the groove of a holder for general powder, the sample surface is smoothed using a slide glass, the sample height is filled so that it matches the edge of the holder, and then the FDS is measured for 0.3°, 2θ=10° to 80° at 0.25 seconds every 0.01°. Phase analysis identifies the phase existing in the sample by comparing it with the database in the Bruker TOPAS program, and uses the entire peaks of the measurement range during fitting. Peak shape utilizes the crystal group and lattice constant of the material and is fitted using only the Lorenzian contribution as the First Principle (FP) among the peak types available in TOPAS.

[0054] Dry electrodes go through various processes, from the mixing process that forms a composite material composition, to the kneading process that kneads the composite material composition to form a mixed aggregate, to the crushing process that crushes the mixed aggregate after kneading, and to the sheeting process that produces electrode powder from the crushed mixed aggregate. As such, the mechanical properties, appearance characteristics, and the performance of the electrode and secondary battery are affected by various factors. In particular, the kneading process in which the binder is fiberized can vary in the degree of fiberization of the binder even with a small change in the process conditions, and the degree of fiberization can also vary depending on the binder crystal size. In addition, the process conditions for applying the kneading process also vary significantly depending on the crystal size, making it very difficult.

[0055] Accordingly, in this specification, when applying the usual mixing process conditions, it is intended to provide an electrode composite composition having excellent mechanical properties by having an excellent degree of fiberization independently of the mixing process conditions and by having a hard binder and a soft binder coexisting and being appropriately harmonized within the binder matrix of a dry electrode.

[0056]

[0057] In one aspect, the electrode composite composition comprises a binder mixture comprising binders having different crystal sizes, and is specifically characterized by comprising a macrocrystalline binder having a crystal size of 50 nm or more and a small-crystalline binder having a crystal size of less than 50 nm.

[0058] Meanwhile, the binder matrix within a dry electrode has not been clearly identified in terms of its internal structure or degree of fiberization to achieve optimal performance. However, the present invention aims to demonstrate that, rather than having the degree of fiberization of the binder within the electrode composite film be uniform throughout and not distinguishing between hard and soft portions, it is preferable for binders with different degrees of fiberization to form specific regions and for these regions to be distributed with appropriate uniformity.

[0059] That is, it can be confirmed that the degree of fiberization is different depending on the crystal size of the binder within the binder matrix, and that, depending on the degree of fiberization, a large-crystal binder can provide strength by imparting hard properties to the film, and a small-crystal binder can provide flexibility by imparting soft properties to the film. This can be achieved by mixing binders having different crystal sizes.

[0060] In one aspect, the binder mixture in the electrode composite composition includes a large-crystal binder having a crystal size of 50 nm or more and a small-crystal binder having a crystal size of less than 50 nm. When the crystal size of the large-crystal binder is less than 50 nm, that is, when there is no binder having a crystal size of 50 nm or more among the mixed binders, the degree of fiberization is not distinguished through mixing, and there is a tendency for excessive fiberization, which may result in low tensile strength and poor durability. In addition, when the crystal sizes of all the mixed binders are 50 nm or more, the mixing time required for an appropriate level of fiberization is long, which may result in poor processability and low flexural strength of the film, which may cause breakage when wound on a calendaring roll, and further, the mechanical properties of the electrode composite film may be poor.

[0061] Preferably, the macrocrystalline binder may have a crystal size of 50 nm to 100 nm, more preferably, the macrocrystalline binder may have a crystal size of 100 nm or less, 90 nm or less, 80 nm or less, or 75 nm or less, and may also be 50 nm or more. The small-crystal binder may have a crystal size of 10 nm to 49 nm, more preferably, 20 nm or more, 25 nm or more, or 30 nm or more, and may be 45 nm or less, or 40 nm or less.

[0062]

[0063] In one aspect, the weight fraction of the large-crystal binder in the binder mixture may be smaller than the weight fraction of the sintered-crystal binder. That is, by utilizing the fast fiberization speed of the sintered-crystal binder, by including an excessive amount of the sintered-crystal binder, when the large-crystal binder and the sintered-crystal binder are fiberized simultaneously, ductility that may be lacking due to slow fiberization of the large-crystal binder can be secured, and even if the large-crystal binder is not completely fiberized, rigidity can be secured through this, so that simultaneous improvement of tensile strength and elongation as mechanical properties can be expected.

[0064] Preferably, with respect to 100 parts by weight of the binder mixture, 5 to 45 parts by weight of the macrocrystalline binder and 55 to 95 parts by weight of the sintered binder may be included. More preferably, the macrocrystalline binder may be 7 parts by weight or more, or 10 parts by weight or more, and may also be 40 parts by weight or less, 35 parts by weight or less, or 30 parts by weight or less. In addition, the sintered binder may be the remainder of 100 parts by weight of the binder mixture. When the macrocrystalline binder and the sintered binder are mixed in the above range, the effect of simultaneously improving tensile strength and elongation may be more outstanding.

[0065] In one aspect, the binder mixture may have an R of 1.27 or less, as defined by the following equation 1.

[0066] [Formula 1]

[0067] R = [C L x (1+W L )] / [(C S x (1+W S )]

[0068] In the above equation 1, C L and C S are the crystal sizes of the macrocrystal binder and the small-crystal binder, respectively, in nm, and W L and W S are the weight fractions of the large-crystal binder and the small-crystal binder, respectively, based on the total weight of the binder mixture.

[0069] R, defined by the above equation 1, can be said to be a factor that can predict the degree of fiberization by influencing the weight fraction according to crystal size in the binder mixture.

[0070] Preferably, the R value may be 1.25 or less, 1.23 or less, 1.22 or less, 1.21 or less, or 1.20 or less, 1.18 or less, or 1.17 or less, and when the R value is within the above range, the mixing ratio can be optimized depending on the crystal size, so that improvement in the mechanical properties of the film, improvement in the fairness of the calendaring process, and even improvement in the performance of the secondary battery can be expected.

[0071]

[0072] In one aspect, the binder is not limited to a specific one as long as it can form a matrix within the electrode composite film, and for example, a fiberizable binder can be applied. The fiberization refers to a process of dividing a polymer into small pieces. For example, it can be performed using a mechanical shear force, etc., and the surface of the fiberized polymer fiber is released to generate a large number of fine fibers (fibrils). The fiberizable binder may preferably include at least one selected from the group consisting of polytetrafluoroethylene (PTFE) and polyolefin, more preferably polytetrafluoroethylene (PTFE), and even more preferably polytetrafluoroethylene (PTFE). Specifically, the polytetrafluoroethylene (PTFE) may be included in an amount of 60 wt% or more based on the total binder weight. At this time, the binder may additionally include at least one of PEO (polyethylene oxide), PVdF (polyvinylidene fluoride), PVdF-HFP (polyvinylidene fluoride-cohexafluoropropylene), and a polyolefin-based binder.

[0073] The above binder mixture may be included in an amount of 0.1 wt% to 10.0 wt% based on the total weight of the electrode composite composition, and preferably, may be included in an amount of 0.2 wt% or more, 0.3 wt% or more, 0.5 wt% or more, 0.7 wt% or more, or 1.0 wt% or more, and may also be included in an amount of 9.0 wt% or less, 8.0 wt% or less, 7.0 wt% or less, or 5.0 wt% or less. In the case of the binder mixture, when included in the above range, there may be no problem with resistance or fiberization for manufacturing in the form of a self-supporting sheet.

[0074]

[0075] In one aspect, the electrode composite composition includes an electrode active material other than the binder, and may further include a conductive material in some cases.

[0076] There is no particular limitation on the above electrode active material as long as it is a commonly used electrode active material. For example, the above electrode active material may be a positive electrode active material or a negative electrode active material.

[0077] The above positive electrode active material may include a lithium transition metal compound containing at least one selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe), which is a compound capable of reversible intercalation and deintercalation of lithium.

[0078] Specifically, it may include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum. More specifically, the lithium metal oxide is a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-Z Ni ZO4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2 (here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(wherein, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (wherein, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.), lithium iron phosphate (e.g., Li 1+a Fe 1-x M x (PO 4-b )X b (Here, M is at least one selected from Al, Mg, and Ti, X is at least one selected from F, S, and N, -0.5≤a≤0.5, 0≤x≤0.5, 0≤b≤0.1), and any one or two or more compounds thereof may be included.

[0079] Among these, the lithium metal oxides are LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni)) in that they can improve the capacity characteristics and stability of the battery. 1 / 3 Mn 1 / 3 Co 1 / 3 )O2, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni) 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 and Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), lithium nickel cobalt aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), or lithium nickel manganese cobalt aluminum oxide (e.g. Li(Ni 0.86 Co 0.05 Mn 0.07 Al 0.02 )O2), lithium iron phosphate (e.g., LiFePO4), etc., and any one of these or a mixture of two or more thereof may be used.

[0080] The above negative active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0081] As the carbon material capable of reversibly intercalating / deintercalating the lithium ions, any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries can be used without particular limitation, and representative examples thereof include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0082] As the above metal or an alloy of these metals with lithium, a metal selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn or an alloy of these metals with lithium may be used.

[0083] The above metal composite oxides include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3(0≤x≤1), Li x WO2(0≤x≤1) and 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, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 로 이루어진 군에서 선택되는 것이 사용될 수 있다.

[0084] Materials capable of doping and dedoping the above lithium include Si, SiO x(0 <x≤2), Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님), Sn, SnO2, Sn-Y(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 상기 원소 Y로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po 및 이들의 조합으로 이루어진 군에서 선택될 수 있다.

[0085] Examples of the above transition metal oxides include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0086] The electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the electrode composite composition, preferably 85 wt% or more, 88 wt% or more, 90 wt% or more, 92 wt% or more, 93 wt% or more, or 95 wt% or more, and may also be included in an amount of 98.5 wt% or less, 98 wt% or less, or 97.5 wt% or less. When included in the above range, it may be preferable in terms of both increasing the capacity and energy density of the electrode and optimizing the functions of the conductive material and binder, which are auxiliary materials.

[0087] The conductive agent is a component for further improving the conductivity of the electrode active material, and the conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives. Specifically, the conductive agent may include at least one selected from the group consisting of activated carbon, graphite, carbon black, and carbon nanotubes (CNTs) for uniform mixing of the conductive agent and improvement of conductivity.

[0088] The conductive agent may be included in an amount of 0.1 wt% to 10.0 wt% based on the total weight of the electrode composite composition. Preferably, it may be included in an amount of 0.2 wt% or more, 0.3 wt% or more, 0.5 wt% or more, or 0.7 wt% or more, and may also be included in an amount of 8.0 wt% or less, 6.0 wt% or less, or 5.0 wt% or less. The more the conductive agent is added, the more advantageous it is for conductive path formation. However, the capacity may be reduced due to a relative decrease in the amount of active material, and it is not easy to control the amount added due to dispersion issues. However, by optimizing the dispersibility within the above range, the effect of conductive path formation can be maximized, so it may be preferable to apply the conductive agent within the above range.

[0089]

[0090] The above electrode composite film may have a porosity of 20% to 50% by volume, specifically 20% to 40% by volume, and more specifically 25% to 35% by volume. When the above range is satisfied, the electrolyte impregnation is excellent, so that the life characteristics and output characteristics can be improved, and the energy density can be excellent.

[0091] The above porosity can be obtained by measuring the apparent density of the electrode composite film and using the actual density calculated based on the actual density and composition of each component, as shown in Equation 3 below.

[0092] [Relationship 1]

[0093] Porosity (%) = [1 - {(apparent density) / (actual density)}] x 100

[0094]

[0095] Method for manufacturing dry electrodes

[0096] In another aspect, a method for manufacturing an electrode composite film is characterized by including a step (S1) of manufacturing an electrode composite composition by mixing an electrode active material, a conductive material, and a binder mixture including a large-crystal binder having a crystal size of 50 nm or more in the binder and a small-crystal binder having a crystal size of less than 50 nm in the binder; a step (S2) of kneading the electrode composite mixture while applying a shear force to obtain a mixed aggregate; a step (S3) of pulverizing the mixed aggregate to obtain an electrode powder; and a step (S4) of roll-rolling the electrode powder to form a sheet to manufacture an electrode composite film.

[0097]

[0098] Since the description of the above electrode active material, conductive material and binder, particularly the binder and binder mixture capable of forming a matrix, is the same as described above, a detailed description is omitted, and the manufacturing process for each step is described below.

[0099]

[0100] S1 stage

[0101] In the above method for manufacturing a dry electrode, the S1 step is a step of manufacturing an electrode composite composition by mixing an electrode active material, a conductive material, and a binder mixture including a large-crystal binder having a crystal size of 50 nm or more and a small-crystal binder having a crystal size of less than 50 nm.

[0102] At this time, the mixing is performed so that the electrode active material, conductive material, and binder mixture can be uniformly distributed, and since they are mixed in a powder form, they can be mixed by various methods without limitation as long as they enable simple mixing thereof. However, since the present invention is manufactured as a dry electrode that does not use a solvent, the mixing can be performed by dry mixing, and the materials can be mixed by putting them into a device such as a mixer or blender.

[0103] At this time, the mixing can be performed in a mixer at 300 rpm to 10,000 rpm for 1 to 60 minutes, preferably 400 rpm or more, or 500 rpm or more, and further, 9,000 rpm or less, 7,000 rpm or less, 5,000 rpm or less, 4,000 rpm or less, or 3,000 rpm or less. In addition, the mixing time can be 2 minutes or more or 3 minutes or more, and further, can be performed for a time of 50 minutes or less, 40 minutes or less, or 30 minutes or less. When performed within the above range, the materials can be uniformly mixed, thereby improving battery performance. More specifically, the mixing speed may be 5,500 rpm or more, 6,000 rpm or more, or 6,500 rpm or more, and may also be 14,000 rpm or less, 13,000 rpm or less, or 12,000 rpm or less.

[0104] The control conditions of the above mixing process can determine how uniformly the binder is fiberized in the subsequent mixing process of step S2. If the mixing is not uniform, even if fiberization occurs uniformly, non-uniform parts may occur on the entire side of the film. Therefore, it may be desirable to perform the mixing process under the conditions described above.

[0105]

[0106] S2 stage

[0107] In the method for manufacturing the above dry electrode, step S2 includes applying a shear force to the composite mixture obtained from the mixing in step S1 to form a mixed aggregate. That is, step S2 may be a fiberization process of a binder mixture using a binder capable of forming a matrix.

[0108] The above fiberization process can be performed, for example, through mechanical milling or kneading, and there are no particular limitations as long as it is generally performed, but preferably, it can be performed through high-temperature, low-shear kneading, and can be performed through a kneader such as a twin-screw extruder. By this kneading, the fiberizable binder is fiberized, thereby combining or linking the electrode active material and conductive powders, so that a mixed aggregate with a solid content of 100% can be formed.

[0109] The above mixing can be performed at a speed of 10 rpm to 100 rpm, and preferably at a speed of 20 rpm to 70 rpm. In addition, the mixing time (t K ) may be 10 to 30 minutes, preferably 15 to 25 minutes or 17 to 25 minutes. When the above range is satisfied, appropriate fiberization can proceed, and a structurally stable matrix can be formed while being uniformly fiberized overall.

[0110] In addition, the above mixing can be performed under conditions of high temperature and pressure higher than atmospheric pressure, and more specifically, under conditions of pressure higher than atmospheric pressure.

[0111] More specifically, the mixing can be performed at a temperature of 50°C to 230°C, preferably 90°C to 200°C. When mixing is performed at a high temperature such as the above range, the fiberization and lump formation of the binder through mixing can be effectively achieved, and the problem of breakage of the fiberized binder can be appropriately prevented.

[0112] In addition, it can be performed at a pressure higher than atmospheric pressure, specifically at a pressure of 1 atm to 3 atm, more specifically at 1.1 atm to 3 atm. When performed within the above range, the problem of breakage of the binder in which fiberization has progressed can be appropriately prevented, and the problem of the density of the aggregates becoming too high can be prevented.

[0113] That is, when a high-temperature, low-shear mixing process is performed under high-temperature and higher-than-normal pressure conditions instead of high-shear mixing, the effect intended by the present invention can be achieved.

[0114] In one aspect, it may be desirable to control the manufacturing method of the dry electrode so that T, defined by the following equation 2, is 5.5 minutes or less.

[0115] [Formula 2]

[0116] T = {[C L x (1+W L )] / [(C S x (1+W S )]} / t K

[0117] In the above equation 1, C L and C S are the crystal sizes of the macrocrystal binder and the small-crystal binder, respectively, in nm, and W L and W Sare the weight fractions of the large-crystal binder and the small-crystal binder, respectively, based on the total weight of the binder mixture, and tK is a unitless number of minutes (min) for the kneading time.

[0118] The aforementioned R value and mixing time t K In terms of the ratio of values, it can be 5.7 minutes or less, 5.6 minutes or less, 5.5 minutes or less, or 5.4 minutes or less, which may mean the fiberization time required depending on the binder mixture, reflecting the influence of the crystal size and weight fraction of the binder mixed in the general kneading time.

[0119] Accordingly, when the T value is controlled to satisfy the above range, for example, when the R value is relatively large, the mixing time can be controlled to be long, and when the R value is relatively small, the mixing time can be controlled to be short, and since the R value can be controlled by determining the crystal size and the mixing ratio, it can be a method for manufacturing an electrode composite film having excellent characteristics.

[0120]

[0121] S3 stage

[0122] In the above method for manufacturing a dry electrode, the S3 step is a step of obtaining powder for an electrode by crushing a mixed aggregate manufactured through a kneading step.

[0123] The mixed aggregates produced through the above mixing process can be directly pressed and formed into sheets (sheeting, e.g., through a calendaring process). However, in this case, the aggregates must be pressed under strong pressure and high temperature to be produced in the form of a thin film. This may result in problems such as the film density becoming too high or the inability to obtain a uniform film. Therefore, the mixed aggregates produced as described above are pulverized to produce powder for electrodes.

[0124] The device used for the above crushing is not particularly limited, but it can preferably be performed by a device such as a blender or grinder.

[0125] The above grinding can be performed at a speed of 1,000 rpm to 15,000 rpm for 5 seconds to 30 minutes, preferably at a speed of 3,000 rpm to 8,000 rpm for 30 seconds to 15 minutes. When performed within the above range, sufficient grinding can be achieved to produce powder of a size suitable for film formation, and a large amount of fine powder can be prevented from being generated in the aggregates.

[0126] The aforementioned crushing process not only facilitates proper formation into a free-standing film in the subsequent sheet forming process, but also, to a certain degree, influences all factors affecting CPCI. Therefore, it may be desirable to control the process so that the aforementioned conditions are met.

[0127] The average particle size of the above electrode powder may be 10 µm to 3,000 µm, specifically 50 µm to 1,500 µm, and more specifically 100 µm to 700 µm. When the above range is satisfied, an electrode composite film having a uniform thickness and density can be formed, and excellent electrode composite film properties can be secured.

[0128]

[0129] Meanwhile, the electrode powder may additionally include fillers, although not essential, to suppress electrode expansion. The fillers are not particularly limited as long as they are fibrous materials that do not cause chemical changes in the battery, and examples thereof include at least one selected from olefin polymers such as polyethylene and polypropylene; and fibrous materials such as glass fiber and carbon fiber.

[0130]

[0131] S4 stage

[0132] In the above method for manufacturing a dry electrode, the step S4 is a step of manufacturing an electrode composite film by thermally compressing the electrode powder through roll rolling.

[0133] The above step S4 may be a process of manufacturing an electrode composite film in the form of a self-supporting sheet by heating and compressing the electrode powder obtained as described above using a rolling roll in a roll-to-roll process (calendering process, sheeting process) including two or more pairs of rolling rolls.

[0134] The above roll-to-roll process (calender process) may include a roll press section, and the roll press section may have rolling rolls arranged in pairs facing each other, or may have three or more rolls arranged in contact with each other, and a plurality of such rolling rolls may be arranged continuously in the roll press section. When a plurality of rolling rolls are arranged continuously, the temperature and main speed ratio (rotation speed ratio of a pair of rolls) of each roll may be the same or different.

[0135] According to one embodiment of the present invention, the step S4 may include a step (S4a) of pre-sheeting the electrode powder to obtain a powder-sheeting film; and a step (S4b) of sheeting the powder-sheeting film two or more times to produce an electrode composite film. That is, after the powder is converted into a sheet in step S4a, the sheet may be rolled in step S4b to improve strength and satisfy the porosity and loading required for the electrode.

[0136] In particular, the temperature of the rolling roll through which the powder-sheeting film is manufactured in the step S4a may be important, as the temperature (T) of the rolling roll into which the powder for the electrode is first introduced. At this time, the temperature of the rolling roll may be 30°C to 150°C, preferably 40°C or higher, 50°C or higher, 60°C or higher, or 70°C or higher, and may also be 140°C or lower, 130°C or lower, 120°C or lower, 110°C or lower, or 100°C. When the above range is satisfied, when the powder for the electrode containing the fiberized binder is formed into a sheet during mixing, the powders can be more organically connected to each other, and accordingly, the overall binder matrix structure can be formed firmly and uniformly.

[0137] The rotation speed ratio of the rolling rolls provided in the roll-to-roll process of the above step S4 can be appropriately adjusted independently within a range of 1:1 to 1:10. In addition, the manufactured electrode composite film can be put back into the roll press section and subjected to heat pressing 1 to 10 times to adjust it to an appropriate thickness.

[0138]

[0139] dry electrode

[0140] In another aspect, a dry electrode is manufactured according to the method for manufacturing a dry electrode described above. For example, the dry electrode may include a current collector; and an electrode composite film of the present invention formed on the current collector.

[0141] In addition, the above dry electrode can be manufactured by laminating and arranging the electrode composite film manufactured according to the above method on one or both sides of the current collector through a lamination process immediately following the step S4.

[0142] The above lamination may be a step of rolling and attaching the electrode composite film onto a current collector. The above lamination may be performed by a roll press method using a lamination roller, and at this time, the lamination roller may be maintained at a temperature of 20°C to 200°C.

[0143]

[0144] When the above dry electrode is a positive electrode, the current collector may be any conductive material that does not cause chemical changes in the battery, and is not particularly limited. For example, the current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0145] When the above dry electrode is a negative electrode, the current collector is not particularly limited as long as it has high conductivity without causing changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

[0146] The thickness of the above-mentioned collector may be 3 ㎛ to 100 ㎛, preferably 8 ㎛ to 80 ㎛, but is not limited thereto. In addition, fine unevenness may be formed on the surface of the collector to increase the adhesive strength of the composite film.

[0147]

[0148] The above-mentioned collector may be used with a conductive primer coated entirely or partially on the surface to lower resistance and improve adhesion. Here, the conductive primer may include a conductive material and a binder, and the conductive material is not limited to any conductive material, but may be, for example, a carbon-based material. The binder may include a fluorine-based binder (including PVDF and PVDF copolymer), an acrylic-based binder, and an aqueous binder that can be dissolved in a solvent.

[0149]

[0150] secondary batteries

[0151] In another aspect, the secondary battery includes the aforementioned dry electrode. The dry electrode may be manufactured using the aforementioned dry electrode manufacturing method. For example, it may be manufactured by mixing two types of binders with different crystallite sizes.

[0152] The secondary battery may be an all-solid-state secondary battery or a non-aqueous electrolyte secondary battery. The all-solid-state secondary battery may have a structure in which a positive electrode, a solid electrolyte membrane, and a negative electrode are laminated, and the non-aqueous electrolyte secondary battery may have a structure in which a positive electrode, a separator, and a negative electrode are laminated, and may be impregnated with a non-aqueous electrolyte.

[0153] Preferably, the electrode may be a dry positive electrode, and specifically, it may be a secondary battery comprising a dry positive electrode and a negative electrode according to the present invention, and a separator or a solid electrolyte membrane interposed between the electrodes. If only one of the positive electrode or negative electrode is the aforementioned dry electrode, the other electrode may be an electrode manufactured through a conventional wet manufacturing method.

[0154] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0155]

[0156] In addition, the electrolyte may include, but is not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of secondary batteries. For example, the inorganic electrolyte may be a sulfide-based solid electrolyte and / or an oxide-based solid electrolyte.

[0157] Specifically, when the electrolyte is a liquid electrolyte, the electrolyte may include an organic solvent and a lithium salt. The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used.Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0158]

[0159] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in secondary batteries. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of, and the lithium salt is LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2.LiCl, LiI, or LiB(C2O4)2 can be used. The concentration of the lithium salt is preferably within the range of 0.1M to 4.0M, preferably 0.5M to 3.0M, and more preferably 1.0M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0160]

[0161] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, 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-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 10.0 wt% based on the total weight of the electrolyte.

[0162]

[0163] In addition, since the secondary battery stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it is useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0164] Accordingly, in another aspect, a battery box including the secondary battery as a unit cell is provided. The battery box may be a battery module or a battery pack.

[0165] The above battery box can be used as a power source for one or more medium- to large-sized devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0166]

[0167] Example

[0168] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0169]

[0170] Example 1

[0171] LiNi as positive electrode active material 0.81 Co 0.05 Mn 0.12 Al 0.02 O296 g, 1 g of carbon black as a conductive material, 3 g of a binder mixture in which polytetrafluoroethylene (PTFE) with a crystal size of 50 nm and PTFE with a crystal size of 39 nm are mixed in a weight ratio of 1:9 as a binder were put into a blender and mixed at 10,000 rpm for 1 minute to prepare a composite mixture, and then the composite mixture was put into a kneader and kneaded at a rotation speed of 40 rpm at 1.1 atm and 150°C for 17 minutes to prepare an aggregate, and the aggregate was pulverized to prepare a powder for an electrode.

[0172] After that, in the roll-to-roll process, the temperature of the roll into which the electrode powder is introduced is set to 100°C, and the electrode powder is powder-sheeted. After sheeting twice, the electrode powder is laminated with aluminum foil to manufacture a dry electrode in which an electrode composite film is placed on an aluminum current collector.

[0173]

[0174] Example 2

[0175] A dry electrode was manufactured in the same manner as in Example 1, except that a binder mixture of polytetrafluoroethylene (PTFE) with a crystal size of 50 nm and PTFE with a crystal size of 39 nm was mixed in a weight ratio of 3:7, and the composite mixture was put into a kneader and kneaded for 19 minutes to manufacture an aggregate.

[0176]

[0177] Example 3

[0178] A dry electrode was manufactured in the same manner as in Example 1, except that a binder mixture of polytetrafluoroethylene (PTFE) with a crystal size of 65 nm and PTFE with a crystal size of 35 nm was mixed in a weight ratio of 1:9, and the composite mixture was put into a kneader and kneaded for 25 minutes to manufacture an aggregate.

[0179]

[0180] Example 4

[0181] A dry electrode was manufactured in the same manner as in Example 1, except that a binder mixture of polytetrafluoroethylene (PTFE) having a crystal size of 75 nm and PTFE having a crystal size of 49 nm was mixed in a weight ratio of 3:7, and the composite mixture was put into a kneader and kneaded for 24 minutes to manufacture an aggregate.

[0182]

[0183] Example 5

[0184] A dry electrode was manufactured in the same manner as in Example 1, except that a binder mixture of polytetrafluoroethylene (PTFE) with a crystal size of 55 nm and PTFE with a crystal size of 45 nm was mixed in a weight ratio of 4:6, and the composite mixture was put into a kneader and kneaded for 20 minutes to manufacture an aggregate.

[0185]

[0186] Comparative Example 1

[0187] A dry electrode was manufactured in the same manner as in Example 1, except that polytetrafluoroethylene (PTFE) with a crystal size of 50 nm was used instead of the binder mixture, and the composite mixture was fed into a kneader and kneaded for 25 minutes to manufacture an aggregate.

[0188]

[0189] Comparative Example 2

[0190] A dry electrode was manufactured in the same manner as in Example 1, except that polytetrafluoroethylene (PTFE) with a crystal size of 50 nm was used instead of the binder mixture, and the composite mixture was fed into a kneader and kneaded for 17 minutes to manufacture an aggregate.

[0191]

[0192] Comparative Example 3

[0193] A dry electrode was manufactured in the same manner as in Example 1, except that polytetrafluoroethylene (PTFE) with a crystal size of 39 nm was used instead of the binder mixture, and the composite mixture was fed into a kneader and kneaded for 25 minutes to manufacture an aggregate.

[0194]

[0195] Comparative Example 4

[0196] A dry electrode was manufactured in the same manner as in Example 1, except that polytetrafluoroethylene (PTFE) with a crystal size of 39 nm was used instead of the binder mixture, and the composite mixture was fed into a kneader and kneaded for 17 minutes to manufacture an aggregate.

[0197]

[0198] Comparative Example 5

[0199] A dry electrode was manufactured in the same manner as in Example 1, except that a binder mixture of polytetrafluoroethylene (PTFE) with a crystal size of 70 nm and PTFE with a crystal size of 50 nm was mixed in a weight ratio of 5:5, and the composite mixture was put into a kneader and kneaded for 25 minutes to manufacture an aggregate.

[0200]

[0201] Comparative Example 6

[0202] A dry electrode was manufactured in the same manner as in Example 1, except that a binder mixture of polytetrafluoroethylene (PTFE) having a crystal size of 39 nm and PTFE having a crystal size of 25 nm was mixed in a weight ratio of 5:5, and the composite mixture was put into a kneader and kneaded for 25 minutes to manufacture an aggregate.

[0203]

[0204] Experimental Example 1: Measurement of physical properties of powder-sheeting films

[0205] The average peel strength and standard deviation of the peel strength of the powder-sheeting film formed during the manufacturing process of the above examples and comparative examples were measured using the following methods.

[0206] 1) Tensile strength (MPa) and elongation (%): After cutting the powder-sheeting film to 50 mm (MD) x 10 mm (TD), the tensile strength was measured in the MD direction of the powder-sheeting film using a UTM device (ZwickRoell) according to the ASTM 638 method, with a preload of 0.01 kg / cm and a speed of 50 mm / min. At this time, the tensile strength (MPa) was calculated as the maximum value of the force applied until the sample did not break, and the elongation (%) was calculated as the ratio of the specimen elongation until breakage occurred compared to the initial length (the ratio of the length just before breakage to the initial length as a percentage).

[0207]

[0208] BB crystal size (C L )BB weight fraction (W L )SB crystal size (C S )SB weight fraction (W S )R-needle time (t) K , min)R / t K Tensile strength (MPa) Elongation (%) Example 1500.1390.90.74174.370.5124.15 Example 2500.3390.70.98195.160.5254.02 Example 3650.1350.91.08254.300.5183.88 Example 4750.3490.71.17244.880.4983.98 Example 5550.4450.61.07205.350.5304.28 Comparative Example 1501---25-0.6322.30 Comparative Example 2501---17-0.4322.00 Comparative Example 3--391-25-0.3522.21Comparative example 4--391-17-0.3804.20Comparative example 5700.5500.51.4178.240.5542.12Comparative example 6390.5250.51.56179.180.3511.95

[0209] BB: Large crystal binder, SB: Small crystal binder

[0210]

[0211] Referring to Table 1 above, in the case of Examples 1 to 5, when a mixture of binders having different crystal sizes and satisfying a specific range of sizes was applied, it can be confirmed that the tensile strength was high and the elongation was also evaluated as high, so that it had the property of being flexible but not easily broken. However, in the case of Comparative Examples 1 to 6, the elongation was low overall, indicating poor flexibility, and accordingly, it can be expected that the processability in the calendaring process was poor due to reduced bending resistance. In the case of Comparative Example 4, which was evaluated as having excellent elongation, it can also be expected that the tensile strength was low, so that it was likely to break when a certain amount of tension was applied.

[0212]

[0213] Experimental Example 2: Battery Performance Evaluation

[0214] 1) Manufacturing of secondary battery: Artificial graphite was used as the negative active material. An anode was prepared including a negative active material layer containing the negative active material, CMC and SBR as negative binders, and carbon black as a negative conductive material in a weight ratio of 96.7:2.8:0.5. The weight loading of the negative active material layer was 277 mg / 25 cm 2 The thickness was 67 ㎛, and a copper foil with a thickness of 10 ㎛ was used as the negative electrode collector.

[0215] The dry positive electrode, the negative electrode, and the porous polyethylene separator of the examples and comparative examples were assembled using a winding method, and an electrolyte (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (volume ratio), lithium hexafluorophosphate (LiPF6 1 mol)) was injected into the assembled battery to manufacture a secondary battery.

[0216] The secondary battery was charged to 3.6 V at a C-rate of 0.1 C and then discharged to 2.5 V to perform an activation process.

[0217] 2) Battery resistance (mΩ): After charging and discharging the secondary battery, and then fully charging and discharging it again, a 2.5C pulse current was applied for a specific time according to the change in SOC, and the surface resistance (0.1 second resistance) was measured.

[0218] 3) Resistance increase rate (%) and capacity retention rate (%): For the above secondary battery, the initial charge and discharge was performed by charging it in CCCV mode at 0.2C until it reached 3.6V (end current 1 / 20C), then discharging it at 0.2C constant current to 2.5V as one cycle, and then performing 100 charge and discharge cycles while measuring the cell resistance and discharge capacity, and calculating the resistance increase rate and capacity retention rate using the formula below.

[0219] Capacity retention rate (%) = (discharge capacity after 100 cycles) / (discharge capacity after 1 cycle) Х100

[0220] Resistance increase rate (%) = [{(100 cycle discharge resistance) / (1 cycle discharge resistance)}-1]Х100

[0221]

[0222] Resistance Increase Rate (%) Capacity Retention Rate (%) Example 12.3599.5 Example 22.5098.9 Example 32.1299.1 Example 42.4599.1 Example 52.5699.3 Comparative Example 14.5096.3 Comparative Example 24.1597.7 Comparative Example 34.3997.5 Comparative Example 44.1596.8 Comparative Example 53.9898.1 Comparative Example 63.8597.5

[0223] Referring to Table 2 above, it can be confirmed that the secondary batteries utilizing the dry electrodes of Examples 1 to 5 were evaluated to have excellent resistance increase rates and capacity retention rates. However, it can be confirmed that the secondary batteries of Comparative Examples 1 to 6 showed a resistance increase approximately twice as large as that of the Examples during cycle operation, and a capacity drop occurred despite the short cycle of 100 cycles.

Claims

1. A binder mixture comprising a large-crystal binder having a crystal size of 50 nm or more and a small-crystal binder having a crystal size of less than 50 nm; and An electrode composite composition comprising an electrode active material.

2. In paragraph 1, An electrode composite composition, wherein the weight fraction of the large-crystal binder in the above binder mixture is smaller than the weight fraction of the small-crystal binder.

3. In paragraph 1, An electrode composite composition, wherein the large-crystal binder has a crystal size of 50 nm to 100 nm, and the small-crystal binder has a crystal size of 10 nm to 49 nm.

4. In paragraph 1, For 100 parts by weight of the above binder mixture, 5 to 45 parts by weight of a large crystal binder and An electrode composite composition comprising 55 to 95 parts by weight of a sintered binder.

5. In paragraph 1, The above binder mixture is an electrode composite composition having R of 1.27 or less, as defined by the following formula 1: [Formula 1] R = [C L x (1+W L )] / [(C S x (1+W S )] In the above equation 1, C L and C S are the crystal sizes of the macrocrystal binder and the small-crystal binder, respectively, in nm, and W L and W S are the weight fractions of the large-crystal binder and the small-crystal binder, respectively, based on the total weight of the binder mixture.

6. In paragraph 1, An electrode composite composition comprising a lithium transition metal compound containing at least one selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe), wherein the electrode active material is a lithium transition metal compound.

7. In paragraph 1, An electrode composite composition, wherein the binder comprises polytetrafluoroethylene (PTFE).

8. A step (S1) of preparing an electrode composite composition by mixing an electrode active material, a conductive material, and a binder mixture including a large-crystal binder having a crystal size of 50 nm or more and a small-crystal binder having a crystal size of less than 50 nm; A step (S2) of kneading the above electrode composite mixture while applying a shear force to obtain a mixed aggregate; Step (S3) of crushing the above mixed aggregate to obtain powder for electrode; and A method for manufacturing a dry electrode, comprising a step (S4) of manufacturing an electrode composite film by rolling the electrode powder into a sheet.

9. In paragraph 8, A method for manufacturing a dry electrode, wherein T is 5.7 min or less, as defined by the following equation 2: [Formula 2] T = {[C L x (1+W L )] / [(C S x (1+W S )]} / t K In the above equation 1, C L and C S are the crystal sizes of the macrocrystal binder and the small-crystal binder, respectively, in nm, and W L and W S are the weight fractions of the large-crystal binder and the small-crystal binder, respectively, based on the total weight of the binder mixture, and t K is a unitless number of minutes (min) for mixing time.

10. In paragraph 9, The above t K A method for manufacturing a dry electrode, the method comprising:

11. In paragraph 8, A method for manufacturing a dry electrode, wherein the roll temperature of the above step S4 is 60°C to 150°C.

12. In paragraph 8, A method for manufacturing a dry electrode, comprising the steps of: (S4a) pre-sheeting the electrode powder to obtain a powder-sheeting film; and (S4b) sheeting the powder-sheeting film two or more times to manufacture an electrode composite film.

13. A secondary battery comprising an electrode manufactured by the dry electrode manufacturing method of Article 8.