Electrode mixture film, manufacturing method therefor, electrode comprising same, and secondary battery comprising same

Abstract

Disclosed in the present specification is an electrode mixture film, which comprises an electrode active material and a binder structured as a three-dimensional fiber network, has a ratio of shear strength in the TD to shear strength in the MD of 0.92-1.08, and has a standard deviation of shear strength of 0.49 or less, wherein the shear strength is measured at two or more points spaced a predetermined interval apart from each other in the depth direction of the electrode mixture film by a surface and interfacial cutting analysis system (SAICAS). Since the three-dimensional network structure of the binder in the electrode mixture film is structurally stable, firm and uniformly formed in the film, an electrode comprising same can have excellent mechanical properties and excellent resistance characteristics, and a secondary battery comprising same can have excellent durability while having improved output and lifespan.

Description

Electrode composite film, method for manufacturing the same, electrode comprising the same, and secondary battery comprising the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0048862, filed April 11, 2024, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Technology field

[0005] The present specification relates to an electrode composite film, a method for producing the same, an electrode including the electrode composite film, and a secondary battery including the same.

[0006]

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] 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.

[0013] Meanwhile, dry electrode films require precise control of mixing, kneading, and calendaring conditions to uniformly disperse and fiberize the binder within the active material to ensure optimal appearance and mechanical properties. However, the lack of a method for quantitatively analyzing the uniform distribution of the active material, conductive agent, and binder within the electrode complicates optimization of process conditions. Furthermore, ensuring reliability in manufacturing high-quality electrodes under optimized process conditions is challenging.

[0014] In addition, dry electrodes exhibit orientation due to the roll-to-roll process performed during the manufacturing process, and there is a problem that cracks may occur in one direction or the electrode may break in a specific direction due to weak mechanical strength depending on this orientation.

[0015] Accordingly, there is a need to develop a dry electrode having excellent appearance characteristics, mechanical properties, and improved resistance by accurately determining the uniformity of the binder within the electrode and optimizing the process conditions for implementing it, thereby achieving superior performance.

[0016]

[0017] One object of the present invention is to provide an electrode composite film having superior mechanical properties and improved resistance characteristics by uniformly distributing a binder within the electrode composite film.

[0018] In addition, another object of the present specification is to provide a method for manufacturing an electrode composite film having the above characteristics by controlling the degree of fiberization of a binder in a mixing process and controlling the adhesion and detachability of powder and rolls in a rolling roll on which powder is sheeted in a sheet forming process.

[0019] In addition, one task of the present specification is to provide an electrode having excellent resistance characteristics and durability due to excellent mechanical properties, and to provide a secondary battery including such an electrode having improved output characteristics and lifespan characteristics.

[0020]

[0021] [1] According to one embodiment of the present specification, an electrode composite film is provided, which includes an electrode active material and a binder having a three-dimensional fiber network structure, wherein the electrode composite film has a ratio of a shear strength in a TD direction to a shear strength in a MD direction of 0.92 to 1.08, a standard deviation of the shear strength is 0.49 or less, and the shear strength is measured at two or more points spaced apart at a constant interval in the depth direction of the electrode composite film by an interface characteristic analysis system (SAICAS).

[0022] [2] In the above [1], the ratio of the shear strength in the TD direction to the shear strength in the MD direction may be 0.95 to 1.05.

[0023] [3] In the above [1] and / or [2], the average value of the shear strength is 15 N / mm 2 Up to 30 N / mm 2 It could be.

[0024] [4] In at least one of the above [1] to [3], the average value of the shear strength is 17 N / mm 2 Up to 25 N / mm 2 It could be.

[0025] [5] In at least one of the above [1] to [4], the standard deviation of the shear strength may be 0.47 or less.

[0026] [6] In at least one of the above [1] to [5], the standard deviation of the shear strength may be 0.45 or less.

[0027] [7] In at least one of the above [1] to [6], the 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).

[0028] [8] In at least one of the above [1] to [7], the binder may include polytetrafluoroethylene (PTFE).

[0029]

[0030] [9] According to another embodiment of the present specification, a method for producing an electrode composite film is provided, comprising: a step (S1) of forming a composite composition by mixing an electrode active material and a fiberizable binder; a step (S2) of kneading the composite composition while applying a shear force for N minutes to form a mixed aggregate; a step (S3) of pulverizing the mixed aggregate to produce an electrode powder; and a step (S4) of sheeting the electrode powder in a roll-to-roll process in which the roll temperature into which the electrode powder is introduced is T℃ to produce a composite film; wherein the product of N and T is 1700 min·℃ to 2500 min·℃.

[0031]

[0010] In the above [9], N may be 15 to 25 minutes.

[0032]

[0011] In at least one of the above [9] and / or

[0010] , the T may be 70°C to 100°C.

[0033]

[0012] In at least one of the above [9] to

[0011] , the step S4 may include a step (S4a) of powder-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 a composite film.

[0034]

[0013] In at least one of the above [9] to

[0012] , the powder-sheeting film has an average value of shear strength of 2.5 N / mm. 2 The above is an ideal, standard deviation of shear strength is 0.54 or less, the binder forms a matrix within the electrode composite film, and the shear strength may be measured at two or more points spaced apart at a certain interval in the depth direction of the electrode composite film by an interface characteristic analysis system (SAICAS).

[0035]

[0014] In at least one of the above [9] to

[0013] , the powder-sheeting film has an average value of shear strength of 2.5 N / mm. 2 5.0 N / mm 2 It could be.

[0036]

[0015] In at least one of the above [9] to

[0014] , the powder-sheeting film may have a standard deviation of shear strength of 0.2 to 0.54.

[0037]

[0038]

[0016] According to another embodiment of the present disclosure, an electrode is provided, comprising: a current collector; and the above-described electrode composite film disposed on the current collector.

[0039] In one embodiment, the electrode may be an anode.

[0040]

[0041]

[0017] According to another embodiment of the present specification, a secondary battery including the above-described electrode is provided.

[0042]

[0043] The electrode composite film of the present specification can have excellent durability and resistance characteristics by controlling the degree of fiberization of the binder in the mixing process during manufacturing and controlling the adhesion and detachability of the powder and the roll on the rolling roll on which the powder is sheeted in the sheet forming process, thereby forming a structurally stable three-dimensional fiber network with uniform binder and constant mechanical properties in the MD and TD directions within the film.

[0044] In addition, the electrode of the present specification can improve durability through excellent mechanical properties including the electrode composite film as described above, has excellent structural stability, and a secondary battery including the electrode can have improved output characteristics and life characteristics through the electrode having the above characteristics.

[0045]

[0046] Below, it is explained in more detail.

[0047] Terms or words used in this description 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 idea 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 way.

[0048] In this specification, "volume cumulative particle diameter D 50 "In the particle size distribution curve of silver particles, it means the particle size corresponding to 50% of the volume accumulation amount. The above D 50 For example, it can be measured using the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several mm, and can obtain results with high reproducibility and high resolution.

[0049] In this specification, "average particle diameter" means the arithmetic mean value calculated by measuring the particle diameters of at least 30 particles observed in a scanning electron microscope image when observed at a magnification of 5,000 to 20,000 times using a scanning electron microscope. In this case, the particle diameter means the longest axis diameter of the particle. The above "volume cumulative particle diameter D 50 " and "average particle size" have different measurement methods, but their values ​​can be derived similarly, and the volume cumulative particle size D measured in the powder state 50 The powder may have a similar value to the average particle size observed in the scanning electron microscope image of the electrode after it is manufactured into an electrode, within the error range.

[0050] In this specification, the term "composite composition" means a mixture comprising 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 composite composition.

[0051] In this specification, the “mixed aggregate” is a product of the kneading process (kneading process) according to this specification in which the above composite composition is subjected to a 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 according to this specification with a solid content of 100%.

[0052] In this specification, “electrode powder” may mean a powder-type electrode material that is a material in which the above mixed aggregate is pulverized to form smaller particles and is in a powder form, and includes an electrode active material, a binder, and optionally a conductive material.

[0053] In this specification, the "electrode composite film" may mean an electrode composite layer 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, or in a state of being laminated on a current collector. The term "free-standing" in this specification means that it can maintain its own form without relying on other members and can be moved or handled by itself. The electrode composite film may be formed by compressing electrode powder as described below. For example, the electrode powder may have a shape in which a layered structure is formed by compressing the electrode powder.

[0054] In this specification, the term "powder-sheeting film" refers to a film formed in a sheet form through a powder-sheeting process in which an electrode powder passes through a rolling roll for the first time in a roll-to-roll process (e.g., a calendaring process) before passing through the last rolling roll in the roll-to-roll process. The film may be a self-supporting sheet, but may have relatively weak self-supporting force. Here, the "powder-sheeting" refers to a process in which an electrode powder is formed into a self-supporting sheet form by a rolling roll in the roll-to-roll process, and the "sheeting" refers to a process performed in the process in which the powder-sheeting film is manufactured into an electrode composite film, and may refer to a process in which the powder-sheeting film is rolled.

[0055] In this specification, “dry electrode” means an electrode manufactured without substantially involving a solvent in the manufacturing process, with no solvent or only a very small amount of solvent added, and may mean, for example, an electrode in which an active material layer is supported by forming a support structure through fiberization of a binder or by being compressed under high pressure.

[0056] In this specification, the term "three-dimensional fiber network structure" may refer to a structure that can be formed by fiberization of a binder during the process of forming a sheet into an electrode composite film from a composite composition including an electrode active material and a binder. Specifically, the three-dimensional fiber network structure may refer to various structures in which fine fibers formed by fiberization of the binder form a skeleton, thereby functioning as a support that enables the electrode composite film to be a self-supporting film. In this case, the electrode active material and, optionally, a conductive material may be accommodated within the pores formed in the three-dimensional fiber network structure.

[0057]

[0058] In this specification, each of the electrode composite film, the method for manufacturing the same, the electrode including the same, and the secondary battery including the same includes at least one of the technical features and / or technical configurations described below, and these technical features and / or technical configurations can be combined in various ways.

[0059]

[0060] Electrode composite film

[0061] An electrode composite film according to the present specification comprises an electrode active material and a binder having a three-dimensional fiber network structure, and is characterized in that the standard deviation of shear strength is 0.49 or less, and the ratio of shear strength in the TD direction to shear strength in the MD direction is 0.92 to 1.08.

[0062] The above shear strength is measured at two or more points spaced at a constant interval in the depth direction of the electrode composite film by an interface characteristic analysis system (SAICAS). Specifically, using the interface characteristic analysis system (SAICAS), the blade is horizontally cut at a constant depth in the thickness direction while maintaining a constant angle and speed from the sample surface, and the horizontal force generated during each horizontal cutting process is measured, and then the shear strength (P) can be calculated using the following equation 1.

[0063] [Formula 1]

[0064] P = F h / (wxd o )

[0065] In the above equation 1, P is the shear strength (N / mm 2 ) and F h is the average value of the measured horizontal force (N), w is the width of the blade (mm), and d0 is the horizontal force F h is the depth (mm) from the measured surface. Here, F h is the average value of the horizontal force, which is the average value of the horizontal force measured while cutting at a specific depth during horizontal cutting, and does not mean the average value of the horizontal force measured at multiple points.

[0066] The above shear strength may mean the average value of the shear strength (P) calculated at a specific depth as described above, for example, at two or more measurement points for each depth, and this average value may be calculated for the MD direction, the TD direction, and the entire body. In addition, the standard deviation of the shear strength may be calculated from the following equation 2 for the shear strength calculated for each specific depth.

[0067] [Formula 2]

[0068]

[0069] In the above equation 2, U B is the standard deviation of shear strength, and Si is the shear strength calculated at the ith measurement point from the surface of the sample, and S m is the average value of the shear strength calculated at each measurement point, and n is an integer greater than or equal to 2, which can mean the number of measurements.

[0070]

[0071] Electrode composite films undergo various processes, from the mixing process to form composite compositions, to the kneading process to form composite aggregates by kneading the composite compositions, to the crushing process to form composite aggregates in the form of composite aggregates, and to the sheeting process to form electrode powders from the crushed composite aggregates. As such, the mechanical properties, appearance characteristics, and performance characteristics of the electrodes are affected by various factors. In particular, the mixing process in which the binder is fiberized can vary in the degree of fiberization of the binder even with small changes in process conditions, and the sheeting process for the electrode powder is a roll-to-roll process using a rolling roll, which has a high degree of process difficulty. In addition, since it is a process in which powders are manufactured in the form of sheets without any special solvents, there is a problem that the mechanical properties and appearance characteristics of the manufactured films vary considerably in performance.

[0072] Accordingly, in this specification, by measuring the average shear strength and the standard deviation of the shear strength for a powder-sheeting film before laminating the electrode composite film with a current collector, the process can be optimized by using this inversely, and according to this optimized process, the binder forms a three-dimensional fiber network with uniformity and structural stability within the electrode composite film, thereby providing an electrode composite film with excellent mechanical properties and improved resistance characteristics.

[0073]

[0074] Shear strength

[0075] According to one embodiment of the present specification, the electrode composite film is characterized in that the ratio of the shear strength in the TD direction to the shear strength in the MD direction is 0.92 to 1.08, and the standard deviation of the shear strength is 0.49 or less.

[0076] The uniform distribution of the binder and the formation of a structurally stable three-dimensional network structure can be greatly influenced by the degree of fiberization of the binder during the mixing process and the sheet forming on the rolling rolls where the powder is first sheeted. In addition, the three-dimensional network structure by the binder can be oriented in the MD (machine direction) direction during the manufacturing process by roll-to-roll processes such as powder sheeting and calendaring processes, and this orientation can form a texture in the electrode composite film. This ultimately causes the mechanical properties of the electrode composite film to deviate between the MD and TD directions, and cracks can easily occur in this part, and the contact between the active material and the conductive material, the conductive material and the conductive material, and the active material and the active material can be severed, which can cause an increase in resistance.

[0077] In order to solve this problem, in this specification, the degree of fiberization of the binder is optimized by controlling the factor that can have the greatest influence in the mixing and sheet forming process, and it is possible to provide an electrode composite film having a uniform and structurally stable three-dimensional fiber network structure, which can be defined by the average value of the shear strength and the ratio of the shear strength in the MD direction and the TD direction and the standard deviation of the shear strength.

[0078] The average value of the above shear strength is 15 N / mm 2 Up to 30 N / mm 2 May be, and preferably, 16 N / mm 2 Above, 17 N / mm 2 or 18 N / mm 2 It may be more than 25 N / mm 2 Below, 23 N / mm 2or less, or 20 N / mm 2 It may be below. Usually, even if the binder is uniformly distributed, if the structural stability is not achieved, the mechanical strength is low, especially 15 N / mm. 2 If the thickness is too small, it can weaken the durability of the secondary battery, and even minor external impacts can cause electrode damage or cracking. Therefore, while higher mechanical strength may be desirable, excessively high strength can negatively impact flexibility, leading to a decrease in flexibility. Furthermore, process costs can increase dramatically, undermining price competitiveness. Therefore, appropriate control is necessary.

[0079] The above shear strength may be a ratio of the shear strength in the TD direction to the shear strength in the MD direction of 0.92 to 1.08. As described above, an electrode manufactured by a dry process, especially having a three-dimensional fiber network structure of a binder due to fiberization of the binder, inevitably has a texture, which causes a difference in strength in each direction, and it is generally the case that the strength value in the MD direction is lower than that in the TD direction. However, by controlling the mixing process and the sheet forming process during the manufacturing process, an electrode composite film in which this difference in strength in each direction is minimized can be implemented, and the average shear strength of the electrode composite film implemented in this way can be adjusted so that the ratio of the strength in the TD direction to the strength in the MD direction falls within the above-mentioned range.

[0080] When this range is satisfied, the texture formed in the electrode composite film can be minimized, the possibility of cracks occurring is low, and improvement in resistance can also be achieved. More preferably, the strength ratio can be 0.93 or more, 0.94 or more, 0.95 or more, 0.96 or more, or 0.97 or more, and can also be 1.07 or less, 1.06 or less, 1.05 or less, 1.04 or less, or 1.03 or less.

[0081] In addition, according to one embodiment of the present specification, the electrode composite film may have a standard deviation of shear strength of 0.49 or less, preferably 0.47 or less, more preferably 0.46 or less, 0.45 or less, 0.44 or less, or 0.43 or less. The standard deviation of shear strength ultimately indicates how uniformly the binder is distributed, but it does not simply mean that the distribution itself is uniform, and may mean that it is uniformly distributed while having structural stability.

[0082] For example, as a method to confirm the uniform distribution of the binder, methods such as scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) or X-ray photoelectron spectroscopy (XPS) can be used to confirm the deviation by measuring the content of components at a specific location, but they cannot guarantee that the three-dimensional fiber network structure is firmly formed at that location with a specific texture suppressed. However, as described above, the fact that the shear strength is above a specific value, the ratio of the strength by direction is within a specific range, and the standard deviation is below a specific value means that the same level of cutting force is required throughout the depth in the thickness direction of the electrode, which can mean that it has structural rigidity, no non-uniformity according to direction, and a uniform distribution throughout the film at the same time.

[0083]

[0084] As described above, when the binder is formed uniformly and structurally stable through fiberization within the electrode composite film to form a three-dimensional fiber network structure, the mechanical properties of the electrode itself are excellent, which can improve the durability of the cell. In addition, the matrix with structural stability can minimize the porosity of the electrode and has the advantage of excellent loading and thickness uniformity, so that improvements in energy density and appearance characteristics can be expected. Furthermore, a well-formed binder matrix can affect the impregnation property of the electrolyte, and the resistance characteristics can be improved by minimizing the agglomeration area, and uniform dispersion of the active material and conductive material can also be expected.

[0085]

[0086] An electrode composite film according to one embodiment of the present specification includes an electrode active material and a binder having a three-dimensional fiber network structure, and may optionally further include a conductive material.

[0087]

[0088] electrode active material

[0089] According to one embodiment of the present specification, there is no particular limitation on the electrode active material as long as it is a commonly used electrode active material. For example, the electrode active material may be a positive electrode active material or a negative electrode active material, and preferably, a positive electrode active material.

[0090] 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.

[0091] 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 Z O4 (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., Li1+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.

[0092] 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.

[0093] Meanwhile, the electrode active material may include an anode active material, and the anode active material may be a material capable of reversibly intercalating / deintercalating lithium ions, and may include at least one selected from the group consisting of, for example, lithium metal; a carbon-based active material; a metalloid-based active material including Si or Sn; a metal-based active material including a metal or an alloy of these metals and lithium; a metal composite oxide; and a transition metal oxide.

[0094] As the above carbon-based active material, any material commonly used in lithium-ion secondary batteries may 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 (or low-crystalline) carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0095] The above metalloid active material may be a silicon-based active material and / or a tin-based active material, and the silicon-based active material may 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)으로 이루어진 군에서 선택될 수 있다. 또한 주석계 활물질은, 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.

[0096] As the above metal-based active material, 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 and lithium can be used.

[0097] 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.

[0098] Examples of the above transition metal oxides include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0099] Meanwhile, according to one embodiment of the present specification, the electrode active material may comprise 80 wt% to 99 wt% based on the total weight of the electrode composite film, 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 comprised at 98.5 wt% or less, 98 wt% or less, or 97.5 wt% or less. When comprised within 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.

[0100]

[0101] bookbinder

[0102] In one aspect, the binder has a function of forming a three-dimensional fiber network structure so that the electrode composite film can be self-supporting, and the binder is not specified as being specific as long as it is fiberizable, that is, can form a three-dimensional fiber network structure in the electrode composite film through fiberization and provide pores capable of accommodating an electrode active material and optionally a conductive material.

[0103] The fiberization of the above binder refers to a process of dividing and finely dividing the polymer applied as the binder, and can be performed, for example, by applying a mechanical shear force, etc., and as a result, the surface is loosened and fiberized, thereby forming a plurality of fine fibers, and thereby including a three-dimensional fiber network structure.

[0104] Such a 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 polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), polyacrylic acid (PAA), polyvinyl pyrrolidone (PVP), and a polyolefin-based binder.

[0105] The fiberizable binder may be included in an amount of 0.1 wt% to 10.0 wt% based on the total weight of the electrode composite film, and preferably, 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 further, 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 fiberizable binder, when included in the above range, there may be no problem of acting as resistance or a problem with the degree of fiberization for manufacturing in the form of a self-supporting sheet.

[0106]

[0107] Challenge

[0108] According to one embodiment of the present specification, the electrode composite film may further include a conductive agent, and the conductive agent is a component for further improving the conductivity of the electrode active material. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite or artificial graphite with a highly developed crystal structure; conductive fibers such as carbon fibers (e.g., carbon nanotubes, carbon nanofibers, carbon fibers) or metallic fibers; fluorinated carbon powder; metallic powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive polymers such as polyphenylene derivatives, etc. may be used. Specifically, the conductive agent may include at least one selected from the group consisting of graphite powder, carbon black, and carbon nanotubes for uniform mixing of the conductive agent and improvement of conductivity.

[0109] 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 film. 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 lowered 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 desirable to apply the conductive agent within the above range.

[0110]

[0111] Meanwhile, in the present specification, the electrode composite film may have a porosity of 17% to 30% by volume, preferably 19% or more by volume, or 20% or more by volume, and may also have a porosity of 29% or less by volume, 28% or less by volume, 27% or less by volume, or 26% or less 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.

[0112] The porosity can be calculated using the following mathematical formula A.

[0113] [Mathematical Formula A]

[0114] Porosity (vol%) = {1-(electrode density / true density)} Х 100

[0115] In the above mathematical formula A, the true density is the density of the electrode composite film measured when the electrode composite film is cut to a certain size and pressed with a press device until the thickness of the film does not change, and the electrode density is the density of the electrode composite film measured when the film is cut to a certain size.

[0116]

[0117] Method for manufacturing electrode composite film

[0118] A method for manufacturing an electrode composite film according to the present specification includes a step (S1) of forming a composite composition by mixing an electrode active material and a binder; a step (S2) of kneading the composite composition while applying a shear force for N minutes to form a mixed aggregate; a step (S3) of pulverizing the mixed aggregate to prepare an electrode powder; and a step (S4) of sheeting the electrode powder in a roll-to-roll process in which the roll temperature into which the electrode powder is introduced is T°C to prepare a composite film, wherein the product of N and T is 1700 min·°C to 2500 min·°C.

[0119]

[0120] The description of the above electrode active material and binder, particularly the binder capable of forming a three-dimensional network structure, and the conductive material that may optionally be further included, is the same as described above, so a detailed description is omitted, and the manufacturing process for each step is described below.

[0121]

[0122] S1 stage

[0123] According to one embodiment of the present specification, in the method for manufacturing the electrode composite film, step S1 is a step of obtaining a composite composition by mixing an electrode active material and a binder. At this time, the mixing is performed so that the electrode active material and the binder 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. In addition, the conductive material may be further optionally included. However, since the electrode composite film according to one embodiment of the present specification 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.

[0124] At this time, the mixing can be performed in a mixer at 3,000 rpm to 20,000 rpm for 5 to 60 minutes, and preferably at 5,000 rpm to 15,000 rpm for 10 to 30 minutes. When performed within the above range, the materials can be uniformly mixed, thereby improving battery performance. More specifically, the mixing speed can be 5,500 rpm or more, 6,000 rpm or more, or 6,500 rpm or more, and also 14,000 rpm or less, 13,000 rpm or less, or 12,000 rpm or less can be applied.

[0125] 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.

[0126]

[0127] S2 stage

[0128] According to one embodiment of the present specification, in the method for manufacturing the electrode composite film, the step S2 includes applying a shear force to the composite composition obtained from the mixing in the step S1 for N minutes to form a mixed aggregate. That is, the step S2 may be a fiberization process of a binder using a binder capable of forming a matrix.

[0129] 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.

[0130] 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 (N) can be 10 to 30 minutes, and preferably 15 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, and through the formation of such a stable matrix, it can greatly contribute to achieving the shear strength of the electrode composite film.

[0131] Furthermore, the content of the composite material composition injected during the mixing process can also be controlled. For example, the composite material composition discharged from the mixing process can be injected in an amount of 50 to 150 parts by volume relative to the internal volume of a mixing device such as a kneader, preferably 60 to 140 parts by volume, 70 to 130 parts by volume, or 80 to 120 parts by volume. By controlling the amount of the composite material composition injected during the mixing process in this way, the fiberization of the binder can be controlled, and this can be controlled simultaneously with the conditions of the mixing process, so that the degree to which the binder matrix structure formed according to the degree of fiberization of the binder affects the contact area between active materials can be controlled, and the degree of cohesion of the binder can be controlled.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] That is, according to the present invention, 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 in the present specification can be achieved.

[0136]

[0137] S3 stage

[0138] According to one embodiment of the present specification, in the method for manufacturing the electrode composite film, the step S3 includes pulverizing a mixed aggregate manufactured through a kneading step to obtain a powder for electrodes.

[0139] The mixed aggregates produced through the above mixing process can be directly pressed into a sheet shape (sheeting, e.g., calendaring process). However, in this case, the aggregates must be pressed under strong pressure and high temperature to produce 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 a powder for electrodes.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144]

[0145] Meanwhile, the electrode powder according to the present specification may additionally include fillers to suppress electrode expansion, although this is not essential. The filler is not particularly limited as long as it is a fibrous material that does not cause a chemical change 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.

[0146]

[0147] S4 stage

[0148] According to one embodiment of the present specification, in the method for manufacturing the electrode composite film, the step S4 includes thermally compressing the electrode powder.

[0149] 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.

[0150] 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.

[0151] According to one embodiment of the present specification, the step S4 may include a step (S4a) of pre-sheeting the powder for the electrode to obtain a powder-sheeting film; and a step (S4b) of sheeting the powder-sheeting film two or more times to produce a composite film. That is, after the powder is converted into a sheet in step S4a, the sheet may be rolled through step S4b to improve strength and satisfy the porosity and loading required for the electrode.

[0152] In particular, the temperature of the rolling roll where 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 60°C to 110°C, preferably 70°C to 100°C, and when the above range is satisfied, when the electrode powder 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.

[0153] 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.

[0154]

[0155] Mixing time (N) and temperature (T) of the powder feeding roll for the electrode

[0156] According to one embodiment of the present specification, the product of the mixing time N of step S2 and the temperature T of the roll into which the electrode powder of step S4 is introduced is 1700 min·℃ to 2500 min·℃.

[0157] As described above, in order to manufacture an electrode composite film according to an embodiment of the present disclosure, control of steps S2 and S4 may be more important, and it may be necessary to control the mixing time and the roll temperature simultaneously. For example, when the mixing time is short, the temperature of the roll should be increased at least to help form the structure of the binder matrix, and when the mixing time is long and binder fiberization is excessive, it may be necessary to control the roll temperature to prevent additional fiberization. Accordingly, the product of N and T may be 1700 min·℃ or more, 1750 min·℃ or more, or 1800 min·℃ or more, and may also be 2500 min·℃ or less, 2450 min·℃ or less, or 2400 min·℃ or less. If the mixing time and roll temperature are not controlled and are less than 1700 min·℃, even if the binder is uniformly distributed without any agglomeration, the loading uniformity and thickness uniformity may deteriorate throughout the powder sheeting film, resulting in poor appearance characteristics of the electrode and easy cracking. In addition, if it exceeds 2500 min·℃, problems such as excessive fiberization or overheating of the powder during powder sheeting, which may cause the surface of the powder sheeting film to be intensively subjected to shear force, may occur, resulting in a large difference in the degree of binder fiberization between the inside and outside.

[0158]

[0159] Average shear strength and standard deviation of shear strength of powder-sheeting films

[0160] According to one embodiment of the present disclosure, the powder-sheeting film has an average shear strength of 2.5 N / mm 2 and the standard deviation of the shear strength may be 0.54 or less. Preferably, the powder-sheeting film has an average shear strength of 2.5 N / mm. 2 5.0 N / mm 2The average shear strength of the powder-sheeting film may be 2.6 N / mm, and the standard deviation of the shear strength may be 0.20 to 0.54. More preferably, the average shear strength of the powder-sheeting film may be 2.6 N / mm. 2 Above, 2.6 N / mm 2 Above, 2.7 N / mm 2 Above, 2.8 N / mm 2 or 2.9 N / mm 2 It may be ideal, and also, 4.5 N / mm 2 Below, 4.0 N / mm 2 or less, or 3.5 N / mm 2 may be less than or equal to 0.53. In addition, the standard deviation of the shear strength may be less than or equal to 0.50, less than or equal to 0.48, less than or equal to 0.45, or less than or equal to 0.43.

[0161] The average shear strength and the standard deviation of the shear strength of the above powder-sheeting film can be used as indicators for finely controlling the process conditions to form a uniform and stable structure of the binder matrix for improving the mechanical properties of the electrode composite film, improving the resistance characteristics, etc. In addition, the process conditions controlled so that the average shear strength and the standard deviation of the shear strength satisfy the above ranges can ensure that the average shear strength and the standard deviation of the shear strength of the electrode composite film satisfy the ranges defined herein. In addition, the average shear strength and the standard deviation of the shear strength of the powder-sheeting film can be measured in the same manner as those of the electrode composite film described above.

[0162]

[0163] electrode

[0164] An electrode according to one embodiment of the present disclosure includes an electrode composite film according to one embodiment of the present disclosure described above. Specifically, the electrode may include a current collector; an electrode composite film according to the present disclosure formed on the current collector; and may be a dry electrode.

[0165] Additionally, the electrode according to the present specification can be manufactured by laminating the electrode composite film on one or both sides of a current collector and laminating the resultant product.

[0166] 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.

[0167]

[0168] When the 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 made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0169] When the above 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.

[0170] 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.

[0171]

[0172] 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.

[0173]

[0174] secondary batteries

[0175] A secondary battery according to the present specification may include the electrode described above, wherein the electrode includes a current collector and the electrode composite film described above disposed on the current collector. For example, the secondary battery may include a secondary battery including a liquid electrolyte and an all-solid-state battery including a solid electrolyte.

[0176]

[0177] In the case where the secondary battery according to one embodiment of the present specification is a secondary battery including a liquid electrolyte, a separator may be included between a plurality of electrodes. The separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used as a separator in secondary batteries may be used without particular limitation, 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 also be used. Additionally, a coated separator containing ceramic components or polymeric materials may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0178]

[0179] In addition, the electrolyte used in this specification includes, 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.

[0180] Specifically, 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.

[0181]

[0182] 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.

[0183]

[0184] 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.

[0185]

[0186] In addition, since the secondary battery according to the present specification 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).

[0187] Accordingly, according to another embodiment of the present specification, a battery box including the secondary battery as a unit cell may be provided. The battery box may include a plurality of battery cells as unit cells, and may include packaging that accommodates the plurality of battery cells. Here, the battery box may be, for example, a battery module or a battery pack.

[0188] The battery module or battery pack may be included in an electric device and may be used as a power source for the electric device. The electric device may be, for example, one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0189]

[0190] Example

[0191] Hereinafter, embodiments of the present specification will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0192]

[0193] Example 1

[0194] LiNi as positive electrode active material 0.81 Co 0.05 Mn 0.12 Al 0.02 A composite composition was prepared by mixing 0296 g, 1.8 g of carbon black as a conductive agent, and 2.2 g of polytetrafluoroethylene (PTFE) as a fiberizable binder. The composite composition was then placed in a kneader and kneaded at a rotation speed of 40 rpm at 1.1 atm and 150°C for 21 minutes to prepare an agglomerate, and the agglomerate was pulverized to prepare powder for an electrode.

[0195] 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 to produce a powder-sheeting film (500 μm in thickness). After sheeting twice, the film is laminated with aluminum foil to produce a dry electrode (110 μm in thickness) in which the electrode composite film is placed on an aluminum current collector.

[0196]

[0197] Example 2

[0198] The above composite composition was introduced into a kneader and kneaded at a rotation speed of 40 rpm at a temperature of 150°C and 1.1 atm for 21 minutes to produce an aggregate, and in the roll-to-roll process, the temperature of the roll into which the electrode powder was introduced was set to 90°C to powder-sheet the electrode powder to produce a powder-sheeting film, except that a dry electrode was manufactured in the same manner as in Example 1.

[0199]

[0200] Example 3

[0201] A dry electrode was manufactured in the same manner as in Example 1, except that the above composite composition was introduced into a kneader and kneaded at a rotation speed of 40 rpm at a temperature of 150°C and 1.1 atm for 25 minutes to produce an aggregate, and the temperature of the roll into which the electrode powder was introduced in the roll-to-roll process was set to 70°C to powder-sheet the electrode powder to produce a powder-sheeting film.

[0202]

[0203] Example 4

[0204] A dry electrode was manufactured in the same manner as in Example 1, except that the above composite composition was introduced into a kneader and kneaded at a rotation speed of 40 rpm at a temperature of 150°C and 1.1 atm for 25 minutes to produce an aggregate, and the temperature of the roll into which the electrode powder was introduced in the roll-to-roll process was set to 90°C to powder-sheet the electrode powder to produce a powder-sheeting film.

[0205]

[0206] Comparative Example 1

[0207] The above composite composition was introduced into a kneader and kneaded at a rotation speed of 40 rpm at a temperature of 150°C and 1.1 atm for 21 minutes to produce an aggregate, and in the roll-to-roll process, the temperature of the roll into which the electrode powder was introduced was set to 70°C to powder-sheet the electrode powder to produce a powder-sheeting film, except that a dry electrode was manufactured in the same manner as in Example 1.

[0208]

[0209] Comparative Example 2

[0210] The above composite composition was introduced into a kneader and kneaded at a rotation speed of 40 rpm at a temperature of 150°C and 1.1 atm for 13 minutes to produce an aggregate, and in the roll-to-roll process, the temperature of the roll into which the electrode powder was introduced was set to 100°C to powder-sheet the electrode powder to produce a powder-sheeting film, except that a dry electrode was manufactured in the same manner as in Example 1.

[0211]

[0212] Comparative Example 3

[0213] The above composite composition was introduced into a kneader and kneaded at a rotation speed of 40 rpm at a temperature of 150°C and 1.1 atm for 21 minutes to produce an aggregate, and in the roll-to-roll process, the temperature of the roll into which the electrode powder was introduced was set to 60°C to powder-sheet the electrode powder to produce a powder-sheeting film, except that a dry electrode was manufactured in the same manner as in Example 1.

[0214]

[0215] Comparative Example 4

[0216] A dry electrode was manufactured in the same manner as in Example 1, except that the above composite composition was introduced into a kneader and kneaded at a rotation speed of 40 rpm at a temperature of 150°C and 1.1 atm for 30 minutes to produce an aggregate, and the temperature of the roll into which the electrode powder was introduced in the roll-to-roll process was set to 90°C to powder-sheet the electrode powder to produce a powder-sheeting film.

[0217]

[0218] Comparative Example 5

[0219] The above composite composition was introduced into a kneader and kneaded at a rotation speed of 50 rpm at a temperature of 150°C and a pressure of 1.1 atm for 25 minutes to produce an aggregate, and in the roll-to-roll process, the temperature of the roll into which the electrode powder was introduced was set to 110°C to powder-sheet the electrode powder to produce a powder-sheeting film, except that a dry electrode was manufactured in the same manner as in Example 1.

[0220]

[0221] Comparative Example 6

[0222] LiNi as positive electrode active material 0.81 Co 0.05 Mn 0.12 Al 0.02 O296 g, 1.8 g of carbon black as a conductive agent, and 2.2 g of polyvinylidene fluoride (PVDF) were mixed in an N-methylpyrrolidone (NMP) solvent to prepare a positive electrode slurry, which was then applied to one surface of an aluminum current collector, dried at 130°C, and rolled at a pressure of 3,000 kgf / cm to prepare a positive electrode in a wet manner.

[0223]

[0224] Experimental Example 1: Measurement of physical properties of powder-sheeting films

[0225] The TD direction value, MD direction value, average value, and standard deviation of the shear strength of the powder-sheeting film formed during the manufacturing process of the above examples and comparative examples were measured by the following methods.

[0226] 1) Shear strength: Using an interface characteristic analysis device (DAIPLA WINTES, SAICAS EN-EX), the blade was moved at a constant angle from the surface of the sample (powder-sheeting film with a thickness of 500 ㎛) at a constant speed (horizontal 2.0 ㎛ / s, vertical 0.2 ㎛ / s) and horizontal cutting was performed every 75 ㎛ in the thickness direction, and the horizontal force generated during each horizontal cutting process (using the average value during the measurement) was measured. Then, the shear strength (P) was calculated using Equation 1 below, and the average for each direction and depth and the overall average were obtained for the shear strength values ​​calculated.

[0227] [Formula 1]

[0228] P = F h / (wxd o )

[0229] In the above equation 1, P is the shear strength (N / mm 2 ) and F h is the average value of the measured horizontal force (N), w is the width of the blade (mm), and d0 is the horizontal force F h is the depth (mm) from the measured surface.

[0230] 2) Standard deviation of shear strength: For the shear strength calculated for each specific depth by the method 1) above, the standard deviation was calculated using the following equation 2.

[0231] [Formula 2]

[0232]

[0233] In the above equation 2, U B is the standard deviation of shear strength, and S i is the shear strength calculated at the ith measurement point from the surface of the sample, and S m is the average value of the shear strength calculated at each measurement point (the value calculated in Equation 1 above), and n is an integer greater than or equal to 2 (where n is 6).

[0234] Mixing time (N) (min) Roll temperature (T) (℃) N x T (min·℃) Average shear strength (N / mm) 2 ) Shear strength standard deviation Example 12110021003.000.410 Example 2219018902.900.385 Example 3257017503.300.262 Example 42510025003.500.412 Comparative Example 1217014702.200.310 Comparative Example 21310013002.300.390 Comparative Example 3216012602.150.280 Comparative Example 4309027002.850.550 Comparative Example 52511027503.100.580

[0235] Referring to Table 1 above, it can be confirmed that the comparative examples that did not satisfy the relationship between the mixing time and the roll temperature in the process of manufacturing the powder sheeting film showed lower shear strength or larger standard deviation results compared to the examples. In particular, in the case of comparative examples 1 to 3, the N x T value is small, so the standard deviation is at an appropriate level, but the shear strength is at least 20% lower than that of the examples, and in comparative examples 4 and 5, the N x T value is excessively high, so the standard deviation is large, and it can be confirmed that the uniformity between the inside and outside of the powder sheeting film is poor.

[0236]

[0237] Experimental Example 2: Evaluation of Electrode Composite Film

[0238] The TD direction value, MD direction value, average value, and standard deviation of the shear strength of the electrode composite film among the dry electrodes manufactured in the above examples and comparative examples were measured by the following methods.

[0239] 1) Shear strength: Using an interface characteristic analysis device (DAIPLA WINTES, SAICAS EN-EX), the blade was moved at a constant angle from the surface of the sample (electrode composite film with a thickness of 110 ㎛) at a constant speed (horizontal 2.0 ㎛ / s, vertical 0.2 ㎛ / s) and horizontal cuts were performed every 15 ㎛ in the thickness direction, and the horizontal force generated during each horizontal cutting process (using the average value during the measurement) was measured. Then, the shear strength (P) was calculated using Equation 1 below, and the average for each direction and depth and the overall average were obtained for the shear strength values ​​calculated.

[0240] [Formula 1]

[0241] P = F h / (wxd o )

[0242] In the above equation 1, P is the shear strength (N / mm 2 ) and F h is the average value of the measured horizontal force (N), w is the width of the blade (mm), and d0 is the horizontal force F h is the depth (mm) from the measured surface.

[0243] 2) Standard deviation of shear strength: For the shear strength calculated for each specific depth by the method 1) above, the standard deviation was calculated using the following equation 2.

[0244] [Formula 2]

[0245]

[0246] In the above equation 2, U B is the standard deviation of shear strength, and S i is the shear strength calculated at the ith measurement point from the surface of the sample, and S m is the average value of the shear strength calculated at each measurement point (the value calculated in Equation 1 above), and n is an integer greater than or equal to 2 (where n is 6).

[0247]

[0248] Average shear strength value (N / mm) 2 )TD direction shear strength (N / mm) 2 )MD direction shear strength (N / mm) 2 )MD / TD Shear Strength Standard DeviationExample 118.218.218.30.990.424Example 218.318.118.40.980.415Example 318.518.518.31.010.405Example 419.118.919.20.980.419Comparative Example 117.519.116.51.160.580Comparative Example 217.818.6171.090.525Comparative Example 318.020.117.21.170.515Comparative Example 418.319.517.81.100.495Comparative Example 518.519.516.81.160.510Comparative example 639.9---1.465

[0249] Referring to Table 2 above, it can be confirmed that the electrode composite films of the dry electrodes of Examples 1 to 4 have superior shear strength and lower standard deviation than the electrode composite films of Comparative Examples 1 to 5, resulting in high strength and uniform films. In particular, Comparative Examples 1 to 3 had a similar standard deviation to that of the Examples in the powder sheeting films, but the uniformity was further reduced in the final electrode composite films. In the case of Comparative Examples 4 and 5, it can be confirmed that the electrode composite films had high standard deviations and poor uniformity despite having no advantage in strength compared to the Examples.

[0250] In addition, compared to Comparative Example 6, which is a wet electrode, the strength of the wet electrode was higher, but the standard deviation was three times higher. Therefore, considering the process advantages of the dry electrode, the disadvantage of the defect rate caused by the high standard deviation may have a greater effect than the advantage obtained from the high strength, so it can be understood that it shows better results than the existing wet electrode.

[0251]

[0252] Experimental Example 3: Battery Performance Evaluation

[0253] 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.

[0254] 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.

[0255] 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.

[0256] 2) Cell resistance (mΩ): After charging and discharging the lithium secondary battery, and then fully charging and discharging it again, a 2.5C pulse current was applied for a specific period of time according to the change in SOC, and the surface resistance (0.1 second resistance) was measured.

[0257] 3) Resistance increase rate (%) and capacity retention rate (%): For the secondary battery, after charging in CCCV mode at 0.2C until 3.6V (end current 1 / 20C), and then discharging to 2.5V at 0.2C constant current as one cycle, the initial charge and discharge were performed, and then 100 charge and discharge cycles were performed while measuring the cell resistance (measured using the method in 2 above) and discharge capacity, and the resistance increase rate and capacity retention rate were calculated using the following formulas.

[0258] Capacity retention rate (%) = (discharge capacity after 100 cycles) / (discharge capacity after 1 cycle) Х100

[0259] Resistance increase rate (%) = (100 cycle discharge resistance) / (1 cycle discharge resistance) Х100

[0260]

[0261] Resistance Increase Rate (%) Capacity Retention Rate (%) Example 1 10.5 9 5.8 Example 2 10.2 9 5.2 Example 3 10.6 9 5.4 Example 4 11.0 9 4.9 Comparative Example 1 13.4 9 0.2 Comparative Example 2 13.2 9 0.5 Comparative Example 3 12.9 9 1.2 Comparative Example 4 14.6 9 0.8 Comparative Example 5 13.5 9 1.9 Comparative Example 6 11.9 9 4.9

[0262] Referring to Table 3 above, it can be confirmed that the dry electrodes of Examples 1 to 4 have a lower resistance increase rate and a higher capacity retention rate than the dry electrodes of Comparative Examples 1 to 5, thereby demonstrating superior cell performance. Ultimately, the uniformity and strength of the electrode composite film are directly related to durability, and the uniformity can also affect the acceleration of degradation. If the uniformity is poor and degradation occurs early in some localized areas, the degradation may accelerate from those areas, which may adversely affect the life characteristics. This can be confirmed from the cell life performance of the Examples and Comparative Examples, which did not have a large difference in strength but showed a difference in standard deviation. In addition, Comparative Example 6 showed that the capacity retention rate was equivalent or higher compared to the wet electrode, and the cell resistance increased slightly compared to the Examples. From the results of Comparative Examples 1 to 5, which have a large standard deviation, it can be inferred that the wet electrode of Comparative Example 6, which has a standard deviation more than three times larger than that of the Examples, will also experience accelerated degradation. In addition, considering the process advantages of dry electrodes, it can be understood that it has advantages beyond expectations in that it can achieve an equivalent or higher level of performance while maintaining a competitive edge in unit price.

Claims

1. An electrode composite film comprising an electrode active material and a binder having a three-dimensional fiber network structure, The above electrode composite film has a ratio of shear strength in the TD direction to shear strength in the MD direction of 0.92 to 1.08, and a standard deviation of the shear strength is 0.49 or less. The electrode composite film, wherein the above shear strength is measured at two or more points spaced apart at regular intervals in the depth direction of the electrode composite film by an interface characteristic analysis system (SAICAS).

2. In paragraph 1, An electrode composite film, wherein the ratio of the shear strength in the TD direction to the shear strength in the MD direction is 0.95 to 1.

05.

3. In paragraph 1, The average value of the above shear strength is 15 N / mm 2 Up to 30 N / mm 2 In, electrode composite film.

4. In paragraph 1, An electrode composite film having a standard deviation of the above shear strength of 0.45 or less.

5. In paragraph 1, An electrode composite film 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.

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

7. Step (S1) of forming a composite composition by mixing an electrode active material and a binder; A step (S2) of kneading the above composite composition while applying a shear force for N minutes to form a mixed aggregate; Step (S3) of crushing the above mixed aggregate to produce powder for electrodes; and In a roll-to-roll process in which the roll temperature into which the electrode powder is introduced is T℃, a step (S4) of manufacturing a composite film by sheeting the electrode powder is included; A method for manufacturing an electrode composite film, wherein the product of N and T is 1700 min·℃ to 2500 min·℃.

8. In paragraph 7, A method for manufacturing an electrode composite film, wherein the above N is 15 to 25 minutes.

9. In paragraph 7, A method for manufacturing an electrode composite film, wherein the above T is 70°C to 100°C.

10. In paragraph 7, A method for manufacturing an electrode composite film, 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 a composite film.

11. In paragraph 10, The above powder-sheeting film has an average shear strength value of 2.5 N / mm 2 and the standard deviation of shear strength is 0.54 or less, A method for manufacturing an electrode composite film, wherein the above shear strength is measured at two or more points spaced at a certain interval in the depth direction of the electrode composite film by an interface characteristic analysis system (SAICAS).

12. An electrode comprising a current collector; and an electrode composite film of claim 1 disposed on the current collector.

13. In paragraph 13, The above electrode is a positive electrode.

14. A secondary battery comprising the electrode of clause 12.

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