Electrode and secondary battery comprising same

Abstract

The present specification discloses technology related to an electrode characterized by comprising an electrode active material and a binder having a three-dimensional fiber network structure, wherein the maximum instantaneous absorption rate of an electrolyte in an electrolyte absorption analysis is 1.3 ㎍ / s or more. The electrode has excellent lithium ion mobility and thus can reduce diffusion resistance, thereby enabling high loading, can prevent local degradation of an active material that may occur at a high rate, and enables a secondary battery having excellent output and rapid charging performance.

Description

Electrode and secondary battery including the same

[0001] This specification discloses technology relating to an electrode and a secondary battery including the same.

[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 power or new and renewable energy and backup power storage devices.

[0004] Typically, a secondary battery is manufactured by applying an 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 drying and rolling processes, and then stacking them 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 an electrolyte, and sealing.

[0005] Meanwhile, during the drying process of the electrode active material slurry, defects such as pinholes or cracks may be induced in the electrode active material layer formed on the current collector as the solvent contained in the slurry evaporates. In addition, since the inner and outer parts of the electrode active material slurry are not dried uniformly during the drying process, there is a risk that the electrode quality may deteriorate due to a powder floating phenomenon caused by the difference in solvent evaporation rates, that is, powders in the parts that dry first rise and form a gap with the parts that dry relatively later.

[0006] To solve the above problem, drying devices capable of controlling the evaporation rate of the solvent are being considered so that the inside and outside of the electrode active material slurry can be dried uniformly; however, these drying devices are very expensive and require significant cost and time to operate, which is disadvantageous in terms of manufacturing processability.

[0007] On the other hand, the solvent included in conventional electrode active material slurries is N-methyl-2-pyrrolidone (NMP), which has a high boiling point and requires high thermal energy and a very long drying oven to dry, making it very unfavorable for mass production. In addition, N-methyl-2-pyrrolidone (NMP) is a toxic substance and is harmful to living organisms, so it has the disadvantage of not being environmentally friendly.

[0008] Therefore, there is 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 type electrode composite film, which is manufactured in a sheet form and includes 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 to form fibers, and then calendering the obtained mixture into a film form to manufacture a free-standing film.

[0009] Meanwhile, in order to increase the energy density of battery cells and improve price competitiveness, it is essential to apply high-loading electrodes. However, when the loading is increased in dry electrodes, the diffusion resistance inside the electrode increases, leading to a problem of degraded battery cell performance. In particular, the rate capability (C-rate) at high rates is inferior, resulting in poor rapid charging performance and output characteristics. Additionally, there is a disadvantage that during long-term charging and discharging, reactions occur mainly on the electrode surface, causing localized degradation of the active material.

[0010] Accordingly, research is needed on dry electrodes that can improve diffusion resistance, output characteristics, and rapid charging performance while increasing the loading amount.

[0011]

[0012] In this specification, the aim is to provide a high-loading electrode with improved diffusion resistance characteristics and improved lithium ion mobility by having a three-dimensional fiber network structure formed from a binder within an electrode composite film have relatively large voids in the interior and near the surface, and by having an electrolyte disposed in these voids.

[0013] In addition, the present specification aims to provide a secondary battery with excellent output characteristics and rapid charging performance by applying the electrode, wherein the electrode has improved diffusion resistance and lithium ion mobility.

[0014]

[0015] [1] In one aspect, an electrode is provided that includes an electrode active material and a binder having a three-dimensional fiber network structure, and has a section in which the maximum instantaneous absorption rate of the electrolyte in an electrolyte absorption analysis is 1.3 μg / s or more. The electrolyte absorption analysis is performed by the step (M1) of impregnating a portion of one end of an electrode cut to a width of 20 mm with an electrolyte containing ethyl carbonate and ethyl methyl carbonate in a weight ratio of 45:55, and the step (M2) of measuring the amount of electrolyte absorbed by the electrode for up to 60 minutes using a tensiometer to obtain a graph of the amount of electrolyte absorbed (μg) as a function of time (s), and the maximum instantaneous absorption rate of the electrolyte is derived from the graph.

[0016] [2] In the electrode of [1] above, the electrode may have a range in which the maximum instantaneous absorption rate of the electrolyte in the electrolyte absorption analysis is 1.5 μg / s or more.

[0017] [3] In the electrode of [1] and / or [2] above, the electrode may have a maximum instantaneous absorption rate of the electrolyte measured in the TD direction in the electrolyte absorption analysis that is smaller than the maximum instantaneous absorption rate of the electrolyte measured in the MD direction.

[0018] [4] At least one of the electrodes in [1] to [3] above, the electrode has a loading amount of 700 mg / 25 cm 2 This is the case, and the porosity may be 24% or less.

[0019] [5] In at least one of the electrodes [1] to [4] above, the electrode active material is a positive active material, and the positive active material may comprise a lithium complex metal compound containing one or more selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn) and iron (Fe).

[0020] [6] In at least one of the electrodes [1] to [5] above, the electrode active material is a positive active material, and the positive active material may include a lithium metal phosphate-based compound represented by the following chemical formula 1.

[0021] [Chemical Formula 1]

[0022] Li 1+x [Fe 1-y M y ]PO4

[0023] In the above chemical formula 1, M comprises one or more selected from the group consisting of Mn, Co, Ni, Al, Mg, and Ti, and -0.5≤x≤0.5, 0≤y<1.

[0024] [7] In at least one of the electrodes [1] to [6] above, the binder may include polytetrafluoroethylene (PTFE).

[0025] [8] In at least one of the electrodes [1] to [7] above, the electrode comprises a current collector and an electrode composite film disposed on the current collector, and the electrode composite film may comprise an electrode active material and a binder having a three-dimensional fiber network structure.

[0026] [9] In another aspect, a secondary battery is provided that includes at least one of the electrodes [1] to [8] above.

[0027]

[0028] The electrode described in this specification has a void larger than a normal void in a three-dimensional fiber network structure formed from a binder within an electrode composite film, and a space is secured therein for the electrolyte to remain after impregnation, thereby improving the diffusion resistance of the battery as the mobility of lithium ions is enhanced. In addition, performance degradation can be prevented even when the loading amount of the electrode is increased or the rate capability of the cell is increased, and the charge-discharge reaction of the battery can occur throughout the entire electrode, thereby preventing local degradation of the active material and enabling the realization of a high energy density cell with improved rapid charging performance and output characteristics.

[0029] The secondary battery described in this specification, by including the electrode, can provide a large-capacity battery with high energy density, and can also have excellent output and rapid charging performance by suppressing degradation at high speeds.

[0030]

[0031] Figure 1 is a graph of the amount of electrolyte absorbed over time measured in the TD direction for the electrode of Example 1.

[0032] FIG. 2 is a graph of the amount of electrolyte absorbed over time measured in the MD direction for the electrode of Example 1.

[0033] Figure 3 is a graph of the amount of electrolyte absorbed over time measured in the TD direction for the electrode of Comparative Example 4.

[0034] Figure 4 is a graph of the amount of electrolyte absorbed over time measured in the MD direction for the electrode of Comparative Example 4.

[0035]

[0036] The present invention will be described in more detail below.

[0037] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0038] In this specification, "volume cumulative average particle size D 50 In the particle size distribution curve, it refers to the particle size corresponding to 50% of the cumulative volume. The above D 50 For example, it can be measured using the laser diffraction method. The laser diffraction method generally enables the measurement of particle sizes ranging from the submicron range to several millimeters, and can obtain results with high reproducibility and high resolution.

[0039] In this specification, "average particle size" refers to the arithmetic mean of the particle sizes of at least 30 particles observed in a scanning electron microscope image when observed at a field of view of 5,000 to 20,000x using a scanning electron microscope. In this case, particle size refers to the diameter of the longest axis of the particle. The above "volume cumulative average particle size D" 50 Although " and "average particle size" differ in their measurement methods, their values ​​can be derived similarly, and the volume-cumulative average particle size D measured in the powder state 50 After the powder is manufactured into an electrode, it may have a value similar to the average particle size observed in the scanning electron microscope image of the electrode and the error range level.

[0040] In this specification, "composite composition" refers to a mixture comprising an electrode active material, a binder, and optionally a conductive material, which is physically mixed to form a uniform dispersed phase. As a product of the mixing process according to this specification, it may be a powdered mixture and may substantially not involve a solvent. Here, "substantially not involving a solvent" means that no solvent is introduced or only a minute amount of solvent is introduced during the mixing of the composite composition.

[0041] In this specification, “mixed aggregate” refers to a product of a mixing process (kneading process) according to this specification in which the above composite composition is subjected to shear force and the binder is fiberized, and the powdered mixture is combined or linked with one another to be converted into an aggregate in a dough-like state, which may substantially contain a solid content close to 100%, and in some cases may contain a small amount of solvent.

[0042] In this specification, “powder for electrode” refers to a material in which the mixed aggregate is crushed to form a powder with a smaller particle size, and may mean an electrode material in powder form comprising an electrode active material, a binder, and optionally a conductive material.

[0043] In this specification, the term "electrode composite film" may refer to a free-standing type single sheet manufactured using an "electrode composite" comprising an electrode active material, a conductive material, and a binder without the involvement of a solvent, or an electrode composite layer laminated onto a current collector. In this specification, the term "free-standing type" means that it can maintain an independent form without relying on other components and can be moved or handled on its own. As described below, the electrode composite film may be formed by compressing electrode powder. For example, the electrode powder may have a shape forming a layered structure by being accumulated through compression.

[0044] In this specification, "powder-sheeting film" refers to a sheet-shaped film manufactured through a powder-sheeting process in which powder for electrodes passes through a rolling roll for the first time in a roll-to-roll process, and may be a self-supporting sheet. Here, "powder-sheeting" means that the powder for electrodes is formed into a sheet shape by a rolling roll of a roll-to-roll process, and "sheeting" refers to a process performed during the process of manufacturing the powder-sheeting film into an electrode composite film, and may refer to a process of rolling the powder-sheeting film.

[0045] In this specification, the “three-dimensional fiber network structure” refers to a structure formed by the fiberization of a binder during the process of sheet forming from a composite composition comprising an electrode active material and a binder into an electrode composite film, wherein a plurality of fibers are connected in any direction at a plurality of points. The three-dimensional fiber network structure may refer to various forms of structures capable of functioning as a support that enables the electrode composite film to be a self-standing film, by having a fine fibrous binder form a framework. At this time, the electrode active material and, optionally, a conductive material may be accommodated within the pores formed in the three-dimensional fiber network structure.

[0046]

[0047] In this specification, each of the electrode and the secondary battery including the same comprises one or more of the technical features and / or technical configurations described below, and these technical features and / or technical configurations may be combined in various ways.

[0048]

[0049] electrode

[0050] In one aspect, an electrode may be provided comprising an electrode active material and a binder having a three-dimensional fiber network structure, wherein the maximum instantaneous absorption rate of the electrolyte in an electrolyte absorption analysis is 1.3 μg / s or higher. The electrolyte absorption analysis is characterized by being performed by the step (M1) of contacting a portion of one end of an electrode cut to a width of 20 mm with an electrolyte containing ethyl carbonate and ethyl methyl carbonate in a weight ratio of 45:55, and the step (M2) of measuring the amount of electrolyte absorbed by the electrode for up to 60 minutes using a tensiometer to obtain a graph of the amount of electrolyte absorbed (μg) versus time (s).

[0051] In the case of dry electrodes, when high-loading electrodes are used to improve cell energy density and secure cost competitiveness, various process problems arise due to the increased electrode thickness, and controlling the level of binder fiberization is difficult. Additionally, while dry electrodes have the advantage of not causing problems such as drying cracks, surface craters, binder migration, or adhesion failures that can occur during drying after coating in wet electrode manufacturing, the uniformity is inevitably reduced when mixing in a dry manner. Consequently, there is bound to be a relatively large amount of localized aggregation of the active material and optionally included conductive material, which can lead to an increase in resistance. In particular, since high-loading inevitably necessitates minimizing the increase in electrode thickness by lowering the porosity, the mobility of lithium ions decreases under low porosity, leading to an increase in diffusion resistance.

[0052] However, in the case of an electrode according to one aspect of the present specification, by having a section in which the amount of electrolyte absorbed increases significantly in the electrolyte absorption analysis, a dry electrode with reduced diffusion resistance can be realized even with high loading that increases the thickness of the electrode and lowers the porosity. That is, by creating a relatively large cavity in addition to the pores generally formed in the three-dimensional fiber network structure inside the electrode composite film, such a cavity serves to retain the electrolyte, thereby significantly reducing the path of movement of lithium ions, and thereby, a dry electrode as described above can be realized.

[0053] When the above electrode with reduced diffusion resistance is included in a secondary battery, it exhibits stable charge and discharge performance at high rates despite increasing capacity through high loading, thereby offering excellent output and rapid charging performance, and can also expect the advantage of improved lifespan by preventing local degradation of the active material.

[0054]

[0055] Maximum instantaneous absorption rate of electrolytes

[0056] In one aspect, the electrode is characterized by having a maximum instantaneous absorption rate of the electrolyte of 1.3 μg / s or more in the electrolyte absorption analysis. An electrode having a maximum instantaneous absorption rate of the electrolyte of 1.3 μg / s or more may imply that there is a relatively large cavity within the three-dimensional fiber network structure formed by the binder. That is, even with the same porosity, a difference in the maximum instantaneous absorption rate of the electrolyte in the electrolyte absorption analysis may occur due to differences in internal structure, and from this difference, it may be determined whether the mobility of lithium ions as described above is improved.

[0057] Generally, the existence of large cavities in addition to the voids typically present inside the electrode has been considered a defect, but the inventors intend to provide a dry electrode that significantly improves the mobility of lithium ions by controlling these cavities with an appropriate structure and utilizing them.

[0058] The maximum instantaneous absorption rate of the electrolyte measured in the above electrolyte absorption analysis is 1.3 μg / s or higher, preferably 1.4 μg / s or higher, 1.5 μg / s or higher, 1.6 μg / s or higher, or 1.8 μg / s or higher, and more preferably a range of 2.0 μg / s or higher may appear.

[0059] The maximum instantaneous absorption rate of the electrolyte may refer to a value measured in the TD direction, a value measured in the MD direction, or the average of values ​​measured in both directions. Additionally, the maximum instantaneous absorption rate of the electrolyte may be smaller when the maximum instantaneous absorption rate of the electrolyte in the TD direction is smaller than when the maximum instantaneous absorption rate of the electrolyte measured in the MD direction. If the maximum instantaneous absorption rate of the electrolyte measured from the electrolyte absorption analysis is as described above, it may indicate that a cavity is properly formed within the electrode, and in this case, improvements in output, rapid charging performance, and lifespan performance can be expected from the improvement of lithium ion mobility.

[0060] The above electrolyte absorption analysis may be performed by including the step (M1) of contacting a portion of one end of an electrode cut to a width of 20 mm with an electrolyte containing ethyl carbonate and ethyl methyl carbonate in a weight ratio of 45:55, and the step (M2) of measuring the amount of electrolyte absorbed by the electrode for up to 60 minutes using a tensiometer to obtain a graph of the amount of electrolyte absorbed (μg) versus time (s).

[0061] The M1 step of contacting the electrode sample with the electrolyte may be a step of cutting the sample to a suitable size, for example, a width of 20 mm, and then immersing a part of one end of the sample in the electrolyte so that the electrolyte can be absorbed into the sample.

[0062] When the width of the above sample is set in the MD direction, a measurement value in the TD direction can be derived, and when the TD direction is set in the width, a measurement value in the MD direction can be derived. The length of the above sample can be cut to a length sufficient to measure the amount of electrolyte absorbed, for example, to a length of about 5 cm to 20 cm. In addition, the above electrolyte absorption analysis analyzes the degree to which the electrode composite film, that is, the composite layer placed on the current collector, absorbs the electrolyte. If the sample includes the electrode composite film, there may be no substantial influence depending on whether it is bonded to the current collector or separated.

[0063] The above electrolyte may contain ethyl carbonate and ethyl methyl carbonate as organic solvents in a weight ratio of 45:55, and lithium salts and additives may be optionally included, but the absorption rate of the electrolyte does not change due to the presence of lithium salts and additives. Furthermore, the use of an organic solvent containing ethyl carbonate and ethyl methyl carbonate in a weight ratio of 45:55 implies that the above weight ratio may substantially vary within a range of approximately + / - about 10 weight percent. For example, it may include cases where the two solvents are included in a weight ratio ranging from 35:65 to 55:45. The above two solvents are substantially widely used as organic solvents and are solvents with a relatively fast absorption rate into electrodes or separators; they possess characteristics suitable for electrolyte absorption analysis and can provide more accurate simulation results in that they are not significantly different from the electrolyte components actually applied.

[0064] Step M2, which obtains a graph of the amount of electrolyte absorbed over the above time, may be a step of measuring how much a sample, in which a portion of one end is immersed in the electrolyte, absorbs the electrolyte over time and graphing the result. In this case, the amount of electrolyte absorbed over time may be measured using a tensiometer (e.g., equipment from SEO can be used). The change in the amount of electrolyte absorbed over time, for example, about 20 to 30 minutes after the sample is brought into contact with the electrolyte, can be measured and graphed.

[0065] The maximum instantaneous absorption rate (µg / s) of the aforementioned electrolyte can be derived from the graph of time (s) and electrolyte absorption amount (µg). The graph may be characterized by the observation of a section in which the electrolyte absorption amount per second is very large. Generally, there is no section in which the electrolyte absorption amount changes constantly or rapidly over time, but the electrode described in this specification is characterized by the essential existence of a section in which the electrolyte absorption amount per second changes rapidly, and the electrolyte absorption amount per second may be characterized by having a maximum value of approximately 1.3 µg / s or more as an instantaneous absorption rate.

[0066]

[0067] In one aspect, the electrode may be highly loaded, and even with high loading, as described above, the diffusion resistance is significantly improved so that problems with lithium ion mobility do not occur, thus possessing a significant advantage of improving both capacity and output performance. Specifically, the electrode composite film of the dry electrode has a loading amount of 600 mg / 25 cm 2 It may be abnormal, 630 mg / 25cm 2 Above, 650 mg / 25cm 2 Above, 670 mg / 25cm 2 Above, 700 mg / 25cm 2 Above 720 mg / 25cm 2 Above, 750 mg / 25cm 2Above, 770 mg / 25cm 2 Above, or 800 mg / 25cm 2 It may be above. Typically, when the loading amount is increased to the above range, a problem of increased diffusion resistance due to increased thickness may occur; however, since this problem can be resolved, a secondary battery with excellent performance can be provided even when the loading amount is increased.

[0068] The above electrode composite film may have a porosity of 17 volume% to 30 volume%, preferably 19 volume% or more, or 20 volume% or more, and may also have a porosity of 29 volume% or less, 28 volume% or less, 27 volume% or less, 26 volume% or less, 25 volume% or less, 24 volume% or less, or 23 volume% or less. When the above range is satisfied, the electrolyte impregnation is excellent, so lifespan characteristics and output characteristics can be improved, and it may be excellent in terms of energy density.

[0069] The porosity can be calculated using the following mathematical formula A.

[0070] [Mathematical Formula A]

[0071] Porosity (Volume%) = {1 - (Electrode Density / True Density)} × 100

[0072] In the above mathematical formula A, true density is the density of the electrode composite film measured when the electrode composite film is taken in a certain size and pressed with a press machine 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 taken in a certain size.

[0073]

[0074] In one aspect, the electrode composite film comprises an electrode active material and a binder, and may optionally further comprise a conductive material, wherein the binder has a three-dimensional fiber network structure, and the active material and optionally the conductive material may be accommodated in voids or cavities formed within the three-dimensional fiber network structure. The electrode active material, conductive material, and binder will be described below.

[0075]

[0076] Electrode active material

[0077] In one aspect, the electrode active material is not subject to any particular limitations 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 may be a positive electrode active material.

[0078] The above-mentioned positive active material is a compound capable of reversible intercalation and deintercalation of lithium, and may include a lithium complex metal compound containing one or more selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe).

[0079] Specifically, it may include a lithium composite transition metal oxide comprising lithium and one or more metals such as cobalt, manganese, nickel, or aluminum. More specifically, the lithium composite transition metal oxide may be a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), or a lithium-nickel-manganese-based 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, LiCo1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-Z1 Co Z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(where, 0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )O4 (where 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 each atomic fractions of independent elements, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.) any one or more of these compounds may be included.

[0080] Among these, the lithium metal oxides mentioned above include LiCoO2, LiMnO2, LiNiO2, and 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 It may be )O2), etc., and any one of these or a mixture of two or more of them may be used.

[0081] In addition, the above positive active material may include a lithium metal phosphate-based compound containing iron, specifically lithium iron phosphate, and may be represented, for example, by the following chemical formula 1.

[0082] [Chemical Formula 1]

[0083] Li 1+a Fe 1-x M x PO4

[0084] In the above chemical formula 1, M is one or more selected from Mn, Co, Ni, Al, Mg, and Ti, and -0.5≤a≤0.5, 0≤x<1.

[0085] When the above-mentioned positive electrode active material is a lithium metal phosphate-based compound, particularly a lithium iron phosphate, the disadvantage is that the capacity is relatively smaller compared to lithium nickel-based oxides, even though safety is guaranteed. However, according to one embodiment of the present invention, a dry electrode capable of high loading can be implemented, so it is possible to implement a secondary battery with excellent safety and improved capacity, and excellent cost competitiveness.

[0086] Meanwhile, the electrode active material may include a negative electrode active material, and the negative electrode active material may be a material capable of reversibly intercalating / deintercalating lithium ions, and may include, for example, at least one selected from the group consisting of lithium metal; carbon-based active material; metalloid active material including Si or Sn; metal-based active material including a metal or an alloy of these metals and lithium; metal composite oxide; and transition metal oxide.

[0087] The above carbon-based active material may be used without particular limitation as long as it is commonly used in lithium-ion secondary batteries, and representative examples include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the above crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the above amorphous (or low-crystallinity) carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0088] The above metalloid active material may include silicon-based active materials and / or tin-based active materials, and silicon-based active materials include Si and 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.

[0089] As the above-mentioned 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 may be used.

[0090] 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, Group 1, 2, and 3 elements of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 로 이루어진 군에서 선택되는 것이 사용될 수 있다.

[0091] Examples of the above transition metal oxides include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0092] Meanwhile, according to one embodiment of the present invention, the electrode active material may comprise 80% to 99% by weight based on the total weight of the electrode composite film, preferably 85% or more by weight, 88% or more by weight, 90% or more by weight, 92% or more by weight, 93% or more by weight, or 95% or more by weight, and may also comprise 98.5% or less by weight, 98% or less by weight, or 97.5% or less by weight. When included within the above range, it may be desirable in terms of increasing the capacity and energy density of the electrode, as well as optimizing the functions of the auxiliary materials, such as the conductive material and the binder.

[0093]

[0094] bookbinder

[0095] In one aspect, the binder functions to form a three-dimensional fiber network structure so that the electrode composite film can have the form of a film, and the binder is not specified as being capable of fiberization, that is, if it can form a three-dimensional fiber network structure within the electrode composite film through fiberization and provide a void capable of accommodating an electrode active material and optionally a conductive material.

[0096] The fiberization of the above binder refers to a treatment that divides the polymer applied as a binder into smaller fibers, which can be performed, for example, by applying mechanical shear force, and as a result, the surface is loosened and fiberized, forming multiple microfibers, and thereby can include a three-dimensional fiber network structure.

[0097] The fiberizable binder may preferably include one or more selected from the group consisting of polytetrafluoroethylene (PTFE) and polyolefins, more preferably may include polytetrafluoroethylene (PTFE), and even more preferably may be polytetrafluoroethylene (PTFE). Specifically, the polytetrafluoroethylene (PTFE) may be included in an amount of 60% by weight or more based on the total weight of the binder. At this time, the binder may additionally include one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), polyvinylidene fluoride-cohexafluoropropylene (PVdF-HFP), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), and polyolefin-based binders.

[0098] The above fiberizable binder may be included in an amount of 0.1% to 10.0% by weight relative to the total weight of the electrode composite film, and preferably, may be included in an amount of 0.2% or more, 0.3% or more, 0.5% or more, 0.7% or more, or 1.0% or more by weight, and may also be included in an amount of 9.0% or less, 8.0% or less, 7.0% or less, or 5.0% or less by weight. In the case of the fiberizable binder, if it is included within the above range, problems acting as resistance or problems with the degree of fiberization for manufacturing into a self-supporting sheet form may not occur.

[0099]

[0100] Challenge

[0101] In one aspect, the electrode composite film may further include a conductive material, and the conductive material is a component for further improving the conductivity of the electrode active material. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery. 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-based fibers (e.g., carbon nanotubes, carbon nanofibers, carbon fibers) or metallic fibers; fluorocarbon 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; and conductive polymers such as polyphenylene derivatives may be used. In detail, to ensure uniform mixing of the conductive material and to improve conductivity, it may include one or more selected from the group consisting of graphite powder, carbon black, and carbon nanotubes.

[0102] The conductive material may be included in an amount of 0.1% to 10.0% by weight relative to the total weight of the electrode composite film. Preferably, it may be included in an amount of 0.2% or more, 0.3% or more, 0.5% or more, or 0.7% or more by weight, and may also be included in an amount of 8.0% or less, 6.0% or less, or 5.0% or less by weight. Although a higher amount of the conductive material may be advantageous for forming a conductive path, the capacity may be reduced due to a relative decrease in the amount of active material, and controlling the amount of material is not easy due to dispersion issues; however, since the effect of forming a conductive path can be maximized by optimizing dispersibility within the above range, it may be desirable to apply the conductive material within the aforementioned range.

[0103]

[0104] The whole house

[0105] In one aspect, the electrode further comprises a current collector, and the electrode composite film may be disposed on the current collector.

[0106] The method of laminating the above electrode composite film to one or both sides of a current collector can be manufactured by pressing the electrode composite film of a cut size and the current collector with a press, and by laminating using a rolling roll supplied from a separate supply roll in a roll-to-roll process.

[0107] When the above electrode is a positive electrode, the above current collector may be conductive without causing chemical changes in the battery, and is not particularly limited. For example, the above current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc.

[0108] When the above electrode is a negative electrode, the above 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. may be used.

[0109] The thickness of the above current collector may be 3 μm to 100 μm, preferably 8 μm to 80 μm, but is not limited thereto. In addition, fine irregularities may be formed on the surface of the above current collector to increase the adhesion of the composite film.

[0110] The above-mentioned current collector may be used with a conductive primer coated wholly or partially on the surface to lower resistance and improve adhesion. Here, the conductive primer may comprise a conductive material and a binder, and the conductive material is not limited to any material that exhibits conductivity, but may be, for example, a carbon-based material. The binder may include solvent-soluble fluorine-based (including PVDF and PVDF copolymers), acrylic binders, and water-based binders.

[0111]

[0112] Method for manufacturing an electrode

[0113] In one aspect, a method for manufacturing an electrode comprises the steps of: mixing an electrode active material and a binder to prepare a composite composition (S1); kneading the composite composition while applying shear force to obtain a mixed aggregate (S2); crushing the mixed aggregate to obtain a powder for the electrode (S3); and rolling the powder for the electrode to form a sheet into an electrode composite film (S4).

[0114]

[0115] Since the description regarding the electrode active material and binder above, and the description regarding the characteristics appearing from the electrolyte absorption analysis, are identical to those previously described, a detailed explanation is omitted, and the manufacturing process for each step is described below.

[0116]

[0117] S1 stage

[0118] In one aspect, step S1 of the method for manufacturing the electrode may be 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 may optionally further include a conductive material. Since the mixture is in powder form, the mixing can be performed by various methods that enable simple mixing, without limitation. However, since the present invention is manufactured as a dry electrode that does not use a solvent, the mixing may be performed by dry mixing, and the materials may be mixed by introducing them into a device such as a mixer or blender.

[0119] At this time, the mixing can be performed in a mixer at 3,000 rpm to 20,000 rpm for 3 minutes to 60 minutes, and preferably at 5,000 rpm to 15,000 rpm for 5 minutes to 50 minutes. 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 higher, 6,000 rpm or higher, or 6,500 rpm or higher, and may also be 14,000 rpm or lower, 13,000 rpm or lower, or 12,000 rpm or lower. Additionally, the mixing time may preferably be 40 minutes or less, 30 minutes or less, or 20 minutes or less.

[0120] The control conditions of the above mixing process can determine how uniformly the binder is fiberized in the subsequent mixing process of step S2. Since uneven mixing can result in non-uniform areas on all sides of the film even if fiberization occurs uniformly, it may be desirable to perform the mixing process under conditions as described above.

[0121] The above mixing speed and time can determine the mixing uniformity of the electrode materials, and since the location or amount of cavities formed within the electrode as fiberization proceeds can be determined depending on the uniformity, and thus can affect the characteristics shown in the electrolyte absorption analysis, it may be desirable to control them within an appropriate range.

[0122]

[0123] S2 stage

[0124] In one aspect, the S2 step may include forming a mixed aggregate by applying a shear force for N minutes to the composite composition obtained from the mixing of the S1 step. That is, the S2 step may be a fiberization process of a binder using a binder capable of forming a three-dimensional fiber network structure.

[0125] The above fiberization process can be performed, for example, through mechanical milling or kneading, and there are no special limitations as long as it is generally performed, but preferably, it can be performed by high-temperature, low-shear kneading, and can be performed through a kneader such as a twin-screw extruder, for example. Through such kneading, the fiberizable binder is fiberized, and the electrode active material powders, or optionally powders containing a conductive material, are combined or linked to form a mixed aggregate with 100% solid content.

[0126] 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 minutes to 30 minutes, and preferably 15 minutes to 25 minutes. When the above range is satisfied, appropriate fiberization can proceed, and a structurally stable three-dimensional fiber network structure can be formed while being fiberized uniformly throughout.

[0127] Furthermore, the content of the composite composition introduced into the mixer during the above mixing process can also be controlled. For example, the composite composition discharged from the above mixing process can be introduced in an amount of 80 volume% to 250 volume% relative to the internal volume of a mixer such as a kneader, and preferably 90 volume% or more, 100 volume% or more, 110 volume% or more, 120 volume% or more, or 130 volume% or more, and also 240 volume% or less, 230 volume% or less, 220 volume% or less, 210 volume% or less, or 200 volume% or less.

[0128] The volume ratio of the composite composition to the internal volume of the above-mentioned mixer may be measured when the volume of the composite composition is at atmospheric pressure. For example, the bulk density of the above-mentioned composite composition in powder form may be less than 1.0 kg / L. If, for instance, the bulk density of the powder is assumed to be 0.46 kg / L, then when 10 kg is input, the input volume becomes 21.7 L, and in this case, when the internal volume of the mixer is 10 L, the volume percentage may be 217 volume%. Due to the low bulk density of the above-mentioned composite composition in powder form, it may be compressed by more than twice, and accordingly, the volume percentage can be controlled by considering the bulk density of the powder, the internal volume of the mixer, the degree of compression of the powder, etc.

[0129] In addition, the above mixing can be performed under high temperature and pressure conditions higher than atmospheric pressure, and more specifically, under pressure conditions higher than atmospheric pressure.

[0130] More specifically, the above 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 of the binder and agglomeration by mixing can be effectively achieved, and the problem of breakage of the fiberized binder can be appropriately prevented.

[0131] In addition, it can be performed at a pressure above atmospheric pressure, specifically at a pressure of 1 atm to 3 atm, and more specifically at 1.1 atm to 3 atm. When performed within the above range, the problem of breakage of the binder undergoing fiberization can be adequately prevented, and the problem of the density of the aggregate becoming too high can be prevented.

[0132] The conditions of the series of mixing processes described above are the processes in which the fiberization of the binder occurs most actively throughout the entire process, and the location, amount, and arrangement relationship of pores or voids inside the electrode can be determined, so it may be desirable to control them within the aforementioned range.

[0133]

[0134] S3 stage

[0135] In one aspect, the above S3 step includes grinding the mixed aggregate produced through the mixing step to obtain a powder for the electrode.

[0136] Although the mixed aggregate prepared through the above kneading process may be immediately pressurized to form a sheet (sheeting, e.g., a calendering process), in this case, the aggregate may need to be pressed under high pressure and high temperature to produce a thin film. Consequently, problems may arise where the film density becomes too high or a uniform film cannot be obtained. Therefore, the mixed aggregate prepared as described above is crushed to produce a powder for electrodes.

[0137] The device used for the above grinding is not particularly limited, but preferably can be performed with a device such as a blender or a grinder.

[0138] The grinding above 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 may not be generated in the aggregate.

[0139] In the case of the aforementioned grinding process, the powder sheeting process in the subsequent sheet forming process can be carried out smoothly, and at the same time, the location, amount, and arrangement relationship of pores or voids inside the electrode can be determined according to the degree. Therefore, it may be desirable to control the process to satisfy the conditions described above.

[0140] The average particle size of the above electrode powder may be 10㎛ to 3,000㎛, more specifically 50㎛ to 1,500㎛, and even more specifically 100㎛ to 700㎛. When the above range is satisfied, an electrode composite film with uniform thickness and density can be formed, and excellent electrode composite film properties can be secured.

[0141]

[0142] Meanwhile, the above-mentioned electrode powder may additionally include fillers to suppress the expansion of the electrode, although this is not essential. The fillers are not particularly limited as long as they are fibrous materials that do not cause chemical changes in the battery, but examples include at least one selected from olefinic polymers such as polyethylene and polypropylene; and fibrous materials such as glass fibers and carbon fibers.

[0143]

[0144] S4 stage

[0145] In one aspect, the above S4 step includes rolling the powder for the electrode to form a sheet.

[0146] The above S4 step may be a process of manufacturing an electrode composite film in the form of a self-standing sheet by heat-pressing the electrode powder obtained as described above using a rolling roll in a roll-to-roll process including two or more pairs of rolling rolls.

[0147] The above roll-to-roll process may include a roll press unit where roll rolling is performed. The roll press unit may have rolling rolls arranged in pairs facing each other, or multiple rolling rolls may be arranged in a continuous manner. When multiple rolling rolls are arranged in a continuous manner, the temperature and peripheral speed ratio (ratio of rotational speeds of a pair of rolls) of each roll may be the same or different.

[0148] The above step S4 may include a step of obtaining a powder-sheeting film by pre-sheeting the powder for the electrode (S4a); and a step of manufacturing a composite film by sheeting the powder-sheeting film two or more times (S4b). That is, in step S4a, the powder is converted into a sheet, and then in step S4b, it is rolled to improve strength and satisfy the porosity and loading amount required for the electrode.

[0149] The temperature (T) of the rolling roll into which the electrode powder is first fed may be important, and the temperature of the rolling roll in which the powder-sheeting film is manufactured in step S4a may be 40°C to 150°C. Preferably, it may be 45°C or higher, 50°C or higher, 55°C or higher, 60°C or higher, 65°C or higher, or 70°C or higher, and may be up to 100°C. When the above range is satisfied, the electrode powder containing the fiberized binder can be formed into a sheet during mixing, thereby allowing the powders to be connected more organically, and accordingly, the overall binder matrix structure can be formed robustly and uniformly.

[0150] The peripheral speed ratio between the rolling rolls equipped in the roll-to-roll process of the above S4 step can be appropriately adjusted independently within 1:1 to 1:10. The peripheral speed ratio between the rolls during powder sheeting in the above S4a step can be 1:1.5 to 1:4, and preferably can be controlled to 1:1.5 to 1:3.5 or 1:1.5 to 1:2.5.

[0151] The powder sheeting film produced by the above powder sheeting may undergo one or more heat pressings through the sheeting process (calendering) of step S4b for reasons such as additional fiberization, securing mechanical properties, or controlling porosity. At this time, the peripheral speed ratio between rolls can be appropriately applied within the range of the peripheral speed ratio in powder sheeting, and the number of times can also be appropriately controlled to match the target properties.

[0152] In the middle or at the end of one or more heat pressing processes of the above S4 steps (S4a and S4b), lamination of the current collector and the electrode composite film may be performed. The lamination may be a step of rolling and attaching the electrode composite film onto the current collector, and the lamination may be performed by a roll press method using a lamination roller, wherein the lamination roller may be maintained at a temperature of 20°C to 200°C.

[0153] The above lamination may preferably be performed after one or more heat pressings, and subsequently, a post-rolling process may be performed with one or more additional heat pressings to achieve the desired porosity. When a post-rolling process is performed in this manner, the appearance of the electrode and calendering processability may be superior compared to lowering the porosity in the laminated film state prior to lamination, and it may also contribute to improving lithium ion mobility by improving the absorption characteristics of the electrolyte. Porosity control through additional heat pressing can be achieved by controlling the compression ratio through roll gap adjustment, and the compression ratio can be derived by the following Equation 2.

[0154] [Relationship 2]

[0155] Compression ratio (%) = [(Electrode thickness) - (Roll gap)] / [(Electrode thickness) - (Current collector thickness)]

[0156]

[0157] The above compression ratio may be, for example, 35% to 70%, preferably 40% or more, 42% or more, 45% or more, 47% or more, or 48% or more, and may also be 68% or less, 65% or less, 63% or less, 60% or less, or 59% or less.

[0158] In performing the above S4 step, controlling the gap between rolls, the peripheral speed ratio, and the roll temperature during powder sheeting in step S4a, and controlling the number of calendering cycles during sheeting in step S4b after powder sheeting and the compression ratio through the post-rolling process after lamination, can have a significant effect on the maximum instantaneous absorption rate of the electrolyte of the dry electrode as indicated by the electrolyte absorption analysis.

[0159] By appropriately controlling the above means, it is possible to induce the formation of a relatively large cavity within the electrode composite film of the dry electrode, and by implementing a dry electrode having such an internal structure, a secondary battery with improved performance can be provided.

[0160] For example, in performing the above step S4, two or more roll rollings may be performed at a peripheral speed ratio of 1:1.5 to 1:2, or one or more roll rollings may be performed at a peripheral speed ratio of 1:2 or higher. During the process from powder sheeting to calendering and lamination, it may be desirable to control the peripheral speed ratio between rolls included in the powder sheeting process of step S4a and the calendering process of step S4b as described above. In this case, the three-dimensional fiber network structure formed as the binder is fiberized during the mixing (premixing) and kneading processes is bonded together and further fiberization occurs during the sheet forming process, so that a void can be appropriately formed within the finally formed three-dimensional fiber network structure, thereby improving the mobility of lithium ions.

[0161]

[0162] secondary battery

[0163] In one aspect, the secondary battery may include a dry electrode as described above. For example, the secondary battery may include a secondary battery comprising a liquid electrolyte and an all-solid-state battery comprising a solid electrolyte.

[0164]

[0165] In one aspect, if the secondary battery is a secondary battery containing 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 pathway for the movement of lithium ions. Any separator typically used in secondary batteries may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specifically, a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof may be used. Alternatively, a conventional porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0166] In the case where the above secondary battery is an all-solid-state battery, the above solid electrolyte membrane can be manufactured to perform the function of the above separator.

[0167]

[0168] The above electrolyte may be selected from organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which are usable when manufacturing secondary batteries, but is not limited to these.

[0169] The above electrolyte may include an organic solvent and a lithium salt. The above organic solvent may be used without special limitations as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the above organic solvent may include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, a carbonate-based solvent is preferred, 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 low-viscosity linear carbonate-based compound (e.g., ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferred.

[0170]

[0171] The above lithium salt may be used without special restrictions as long as it is a compound capable of providing 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 - It may be at least one selected from the group consisting of, and the lithium salt is, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2) 2. LiCl, LiI, or LiB(C2O4)2, etc., may be used. It is preferable to use the lithium salt in a concentration 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 falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0172]

[0173] In addition to the above electrolyte components, the above electrolyte may further include one or more additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery, such as, for example, a haloalkylene carbonate-based compound such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additive may be included in an amount of 0.1 to 10.0 weight% based on the total weight of the electrolyte.

[0174]

[0175] battery box

[0176] In another aspect, a battery box comprising a plurality of the above secondary batteries may be provided. The battery box may include a plurality of secondary batteries and may include a packaging that accommodates the plurality of secondary batteries. Here, the battery box may be, for example, a battery module or a battery pack.

[0177] Since the above secondary battery stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it can be usefully applied in portable devices such as mobile phones, laptops, and digital cameras, or in the field of electric vehicles such as Full Electric Vehicles (FEVs) and Hybrid Electric Vehicles (HEVs).

[0178] The above battery box may be used as one or more power devices selected from the group consisting of a power tool; an electric vehicle including a full electric vehicle (FEV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0179]

[0180] According to the present specification, in another aspect, an electric device or electronic device may be provided that includes the battery box, wherein the battery box is included as a power source.

[0181]

[0182] Examples

[0183] Hereinafter, embodiments of the present invention are described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0184]

[0185] Example 1

[0186] 4940 g of LiFePO4 as the positive active material, 20 g of carbon black as the conductive material, and 40 g of polytetrafluoroethylene (PTFE) as the binder were put into a blender and mixed for 10 minutes to prepare a composite composition, then the composite composition was put into a kneader and kneaded at a temperature of 180°C at a rotation speed of 25 rpm for 5 minutes to prepare an aggregate, and the aggregate was ground in a blender at a speed of 10,000 rpm for 1 minute to prepare a powder for the electrode.

[0187] Subsequently, in the above roll-to-roll process, the electrode powder was fed into a lap roll press (roll diameter 200 mm, roll temperature 100℃, speed ratio 20 / 40 rpm) to powder-sheet and produce a powder-sheet film. Then, calendering was performed twice at a speed ratio of 20 / 30 rpm, and the film was laminated with aluminum foil coated with a conductive primer to ensure that the electrode composite film was placed on an aluminum current collector. Afterward, a post-rolling process was performed at a peripheral speed ratio of 1:1 to produce a dry electrode (loading amount 600 mg / 25 cm) with a compression ratio of 48%. 2 , porosity 26%) was manufactured.

[0188]

[0189] *

[0190] Example 2

[0191] Except for feeding the electrode powder into a roll press with a speed ratio of 20 / 45 rpm during powder sheeting, a dry electrode (loading amount 600 mg / 25 cm) was prepared in the same manner as in Example 1 above. 2 , porosity 26%) was manufactured.

[0192]

[0193] Example 3

[0194] Except for feeding the electrode powder into a roll press with a speed ratio of 20 / 30 rpm during powder sheeting and performing a post-rolling process to achieve a compression ratio of 54%, a dry electrode (loading amount 630 mg / 25 cm) was prepared in the same manner as in Example 1 above. 2 , porosity 25%) was manufactured.

[0195]

[0196] Example 4

[0197] Except for feeding the electrode powder into a roll press with a speed ratio of 20 / 30 rpm during powder sheeting and performing a post-rolling process to achieve a compression ratio of 59%, a dry electrode (loading amount 630 mg / 25 cm) was prepared in the same manner as in Example 1 above. 2, porosity 24%) was manufactured.

[0198]

[0199] Example 5

[0200] Except for feeding the electrode powder into a roll press with a speed ratio of 20 / 40 rpm during powder sheeting and setting the peripheral speed ratio to 20 / 25 rpm during two calendering cycles, a dry electrode (loading amount 650 mg / 25 cm) was prepared in the same manner as in Example 1 above. 2 , porosity 25%) was manufactured.

[0201]

[0202] Example 6

[0203] Except for feeding the electrode powder into a roll press with a speed ratio of 20 / 24 rpm during powder sheeting, setting the peripheral speed ratio to 20 / 40 rpm during two calendering passes, performing one additional calendering pass at a peripheral speed ratio of 20 / 22, and not proceeding with the post-rolling process, a dry electrode (loading amount 630 mg / 25cm) was prepared in the same manner as in Example 1 above. 2 , porosity 23%) was manufactured.

[0204]

[0205] Comparative Example 1

[0206] During powder sheeting, the electrode powder is fed into a roll press with a speed ratio of 20 / 24 rpm, and three additional calendering cycles are performed; except that the process is carried out at a speed ratio of 20 / 24 rpm, a dry electrode (loading amount 600 mg / 25 cm) is prepared in the same manner as in Example 1 above. 2 , porosity 26%) was manufactured.

[0207]

[0208] Comparative Example 2

[0209] Except for feeding the electrode powder into a roll press with a speed ratio of 20 / 28 rpm during powder sheeting and performing two additional calendering cycles, and then performing a post-rolling process to achieve a compression ratio of 59% after proceeding at a speed ratio of 20 / 28 rpm, a dry electrode (loading amount 630 mg / 25cm) was prepared in the same manner as in Example 1 above. 2 , porosity 24%) was manufactured.

[0210]

[0211] Comparative Example 3

[0212] During powder sheeting, the electrode powder is fed into a roll press with a speed ratio of 20 / 24 rpm, and two additional calendering cycles are performed; except that the process is carried out at a speed ratio of 20 / 24 rpm, a dry electrode (loading amount 650 mg / 25 cm) is prepared in the same manner as in Example 1 above. 2 , porosity 25%) was manufactured.

[0213]

[0214] Comparative Example 4

[0215] An anode slurry was prepared by mixing 4,940 g of LiFePO4 as the anode active material, 20 g of carbon black as the conductive material, and 40 g of polyvinylidene fluoride (PVDF) as the binder in N-methylpyrrolidone (NMP) solvent. Subsequently, the anode slurry was loaded onto a current collector at a loading amount of 600 mg / 25 cm². 2 An anode with a porosity of 26% was manufactured by applying it, drying it at an average temperature of 150°C, and rolling it.

[0216]

[0217] Comparative Example 5

[0218] A dry electrode was prepared in the same manner as in Example 1, except that 4940 g of LiFePO4 as the positive active material, 20 g of carbon black as the conductive material, and 40 g of polytetrafluoroethylene (PTFE) as the binder were added to a blender and mixed for 1 minute to prepare a composite composition. In the case of Comparative Example 5, due to insufficient mixing, fiberization did not proceed normally from the kneading process, resulting in severe cracking on the side of the final electrode and an uneven electrode with stains visible on the surface, making it impossible to manufacture a good electrode.

[0219]

[0220] Comparative Example 6

[0221] A dry electrode was intended to be manufactured in the same manner as in Example 1, except that the grinding process was not performed. However, in the case of Comparative Example 6, the grinding process was not applied, resulting in a large number of large particles, making it impossible to form a sheet-shaped film during the powder sheeting process.

[0222]

[0223] Experimental Example 1: Electrolyte Absorption Analysis

[0224] The anode prepared in the above examples and comparative examples was cut to a width of 20 mm and a length of 100 mm, and one end of the cut electrode composite film was immersed in an electrolyte for about 0.01 mm. At this time, the electrolyte used was a mixed solvent in which ethyl carbonate and ethyl methyl carbonate were mixed in a weight ratio of 45:55.

[0225] From the moment the cut electrode composite film sample was immersed in the electrolyte, the amount of electrolyte absorbed (μg) by the electrode composite film for 20 minutes was measured through weight change using a tensiometer (SEO), and a graph of the amount of electrolyte absorbed (μg) against time (s) was obtained. The above process was repeated 10 times with samples at different locations, and the average value was used.

[0226] Maximum instantaneous absorption rate of electrolyte (μg / s) TD direction average MD direction average Example 1 2.10 2.51 Example 2 2.21 2.75 Example 3 1.89 1.92 Example 4 1.58 1.66 Example 5 2.52 2.78 Example 6 2.55 3.05 Comparative Example 10.51 0.62 Comparative Example 20.77 0.68 Comparative Example 30.49 0.57 Comparative Example 40.42 0.65 Comparative Example 5 N / AN / A Comparative Example 6 N / AN / A

[0227] Referring to Table 1 above, in the case of Examples 1 to 6, moments when the maximum instantaneous absorption rate of the electrolyte was 1.3 μg / s or higher occurred in both the MD direction and the TD direction. It was confirmed that the electrolyte was absorbed at a constant rate in all cases except for the section where the maximum instantaneous absorption rate occurred, and the results are shown in Figures 1 and 2. Figure 1 is a graph of the amount of electrolyte absorbed over time measured in the TD direction of Example 1, showing the results of three measurements, and Figure 2 is a graph of the amount of electrolyte absorbed over time measured in the MD direction of Example 1, showing the results of three measurements. As can be seen from the graphs, it can be seen that there is a section where the amount of absorption increases instantaneously. On the other hand, in the case of Comparative Examples 1 to 3, it can be confirmed that moments when the maximum instantaneous absorption rate of the electrolyte exceeded 1.0 μg / s were not observed because the peripheral speed ratio of the roll during powder sheeting, the peripheral speed ratio during additional calendering, the compression ratio, and the final porosity were not properly controlled. In addition, in the case of Comparative Example 4, which is a wet electrode, similar to Comparative Examples 1 to 3, there was no moment where the maximum instantaneous absorption rate of the electrolyte exceeded 1.3 μg / s, and it can be confirmed that the electrolyte was absorbed into the sample at a constant rate throughout the entire range, as can be verified through Figures 3 and 4. Figure 3 is a graph of the wet electrode of Comparative Example 4, showing the amount of electrolyte absorbed over time measured in the TD direction, and Figure 4 is a graph of the amount of electrolyte absorbed over time measured in the MD direction of Comparative Example 4. Looking at the graphs in Figures 3 and 4, unlike the graphs in Figures 1 and 2 of Example 1, it can be confirmed that, excluding changes in the noise level, no section where the amount of absorption increased significantly was observed, and the graphs showed a constant upward trend.

[0228]

[0229] Experimental Example 2: Battery Performance Evaluation

[0230] 1) Manufacture of a secondary battery: Artificial graphite was used as the negative electrode active material. A negative electrode was prepared comprising a negative electrode active material layer containing the above negative electrode active material, negative electrode binders CMC and SBR, and negative electrode conductive material carbon black in a weight ratio of 96.7:2.8:0.5. The weight loading amount of the above negative electrode active material layer was 290 mg / 25cm 2 It was 72 μm thick, and a copper foil with a thickness of 8 μm was used as the cathode current collector.

[0231] The dry anode of the example and comparative example, the cathode, and the porous polyethylene separator were assembled using a winding method, and an electrolyte (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (volume ratio)) and lithium hexafluorophosphate (LiPF6 1 mol) were injected into the assembled battery to manufacture a secondary battery.

[0232] The above secondary battery was charged to 3.6V at a 0.1C C-rate, and then discharged to 2.5V to proceed with the activation process.

[0233] 2) Battery resistance (mΩ): After charging and discharging the secondary battery, a 2.5C pulse current was applied for a specific time according to the change in SOC while fully charging and discharging the battery. The diffusion resistance (@30s), DCIR (0.1s, @ SOC 30%), and 10s resistance were measured, and the diffusion resistance was obtained by calculating the difference between the 10s resistance and the DCIR value.

[0234] 3) Relative charging capacity (%) and relative discharging capacity (%): The above secondary battery was charged in CCCV mode until it reached 0.33C and 3.6V (ending current 0.05C) to measure the initial charging capacity, then discharged to 2.5V with a constant current of 0.2C, and then increased the rate to 2C to charge and discharge, and the respective capacities were measured at each time. The measured charging capacity and discharging capacity were expressed as relative ratios to the initial charging capacity.

[0235] Loading amount (mg / 25cm)2 Porosity (vol%) DCIR (mΩ) Diffusion Resistance (mΩ) Initial Charge Capacity (mAh) Relative Charge Capacity (%) Relative Discharge Capacity (%) Example 1 600 267 103 39 110 89.5 83.3 Example 2 600 266 85 334 11 190.7 83.6 Comparative Example 1 600 267 28 356 11 180.6 77.6 Comparative Example 4 (Wet) 600 267 63 366 10 97 6.1 74.5

[0236] Loading amount (mg / 25cm) 2 ) Porosity (vol%) DCIR (mΩ) Diffusion Resistance (mΩ) Initial Charge Capacity (mAh) Relative Charge Capacity (%) Relative Discharge Capacity (%) Example 36 30 257 173 45 115 84.6 77.2 Example 46 30 247 223 51 115 82.4 75.2 Example 66 30 246 923 21 113 95.3 84.6 Comparative Example 26 30 247 35 363 115 78.2 71.4

[0237] Loading amount (mg / 25cm) 2 ) Porosity (vol%) DCIR (mΩ) Diffusion Resistance (mΩ) Initial Charge Capacity (mAh) Relative Charge Capacity (%) Relative Discharge Capacity (%) Example 5 650 257 123 37 120 81.17 3.5 Comparative Example 3 650 257 323 60 120 77.06 9.9 Comparative Example 5 N / AN / AN / AN / AN / AN / AN / AN / A Comparative Example 6 N / AN / AN / AN / AN / AN / AN / AN / A

[0238] Referring to Table 2 above, it can be seen that the resistance values ​​of Examples 1 and 2 are significantly reduced compared to Comparative Examples 1 and 4, and in particular, the diffusion resistance is reduced by about 10%. Furthermore, compared to Comparative Example 4, which uses a wet electrode, Examples 1 and 2 show that the relative charging capacity is more than 10%p higher even at high speeds, indicating excellent capacity retention even during rapid charging. Additionally, the relative discharge capacity at high speeds is also about 10%p higher, indicating significantly excellent output.

Claims

1. Comprising an electrode active material and a binder having a three-dimensional fiber network structure, In the electrolyte absorption analysis, the maximum instantaneous absorption rate of the electrolyte is 1.3 μg / s or higher, and The above electrolyte absorption analysis is, A step (M1) of contacting a portion of one end of an electrode composite film cut to a width of 20 mm with an electrolyte containing ethyl carbonate and ethylmethyl carbonate in a weight ratio of 45:55 and The method is performed by including the step (M2) of measuring the electrolyte absorption amount of the electrode composite film for up to 60 minutes using a tensiometer to obtain a graph of the electrolyte absorption amount (μg) against time (s), and The electrode, whose maximum instantaneous absorption rate of the above electrolyte is derived from the above graph.

2. In Paragraph 1, An electrode having a maximum instantaneous absorption rate of the above electrolyte of 1.5 μg / s or more.

3. In Paragraph 1, The above electrode is an electrode in which the maximum instantaneous absorption rate of the electrolyte measured in the TD direction is smaller than the maximum instantaneous absorption rate of the electrolyte measured in the MD direction.

4. In Paragraph 1, The above electrode has a loading amount of 600 mg / 25 cm 2 An electrode having a porosity of 26% or less.

5. In Paragraph 1, The above electrode active material is a positive electrode active material, and The electrode comprises a lithium composite metal compound containing one or more selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe), wherein the positive electrode active material comprises a lithium composite metal compound.

6. In Paragraph 1, The above electrode active material is a positive electrode active material, and The above positive active material comprises an electrode comprising a lithium metal phosphate-based compound represented by the following chemical formula 1: [Chemical Formula 1] Li 1+a [Fe 1-x M x ]PO4 In the above chemical formula 1, M comprises one or more selected from the group consisting of Mn, Co, Ni, Al, Mg, and Ti, and -0.5≤x≤0.5, 0≤y<1.

7. In Paragraph 1, The above binder comprises polytetrafluoroethylene (PTFE), an electrode.

8. In Paragraph 1, The above electrode comprises a current collector and an electrode composite film disposed on the current collector, and The electrode composite film comprises an electrode active material and a binder having a three-dimensional fiber network structure.

9. A secondary battery comprising the electrode of claim 1.

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