Method for evaluating of slurry dispersion status and method for manufacturing slurry using same

Abstract

A method for evaluating a slurry dispersion status according to one embodiment of the present invention measures an SMD value represented by Equation 1 with respect to a slurry: [Equation 1] SMD = G'1 / G'2. In equation 1, G'1 is an elastic modulus measured after stirring the slurry at shear rate = 1000 / s, and G'2 is an elastic modulus measured after stirring the slurry at shear rate = 10 / s.

Description

Slurry dispersion phase evaluation method and slurry manufacturing method using the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0101241, filed August 2, 2023, and Korean Patent Application No. 10-2024-0101477, filed July 31, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a method for evaluating electrode slurry for a secondary battery and a method for manufacturing a slurry using the same.

[0004] In modern society, the widespread use of portable devices like cell phones, laptops, camcorders, and digital cameras has fueled active development of technologies related to these devices. Furthermore, rechargeable secondary batteries are increasingly being used as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (P-HEVs) to address air pollution caused by conventional gasoline-powered vehicles, further increasing the need for secondary battery development.

[0005] Currently commercialized secondary batteries include nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and lithium secondary batteries. Among these, lithium secondary batteries are receiving attention for their advantages of being able to charge and discharge freely, having a very low self-discharge rate, and having a high energy density, as they have almost no memory effect compared to nickel-based secondary batteries.

[0006] These lithium secondary batteries primarily use lithium oxide and carbon materials as positive and negative electrode active materials, respectively. The lithium secondary battery may include an electrode assembly including a positive electrode and a negative electrode, each coated with the positive and negative electrode active materials, and a separator disposed between the positive and negative electrodes.

[0007] Meanwhile, slurries can be used to manufacture electrodes and separators used in lithium secondary batteries. Slurries can be produced by mixing and processing active material particles, binders, conductive agents, solvents, and other components. The dispersed phase of a slurry varies depending on processing conditions and composition, and the dispersed phase of the slurry is a critical factor that significantly influences the occurrence of process defects.

[0008] Therefore, predicting electrode processability through quantifying the slurry dispersion phase is necessary. Conventionally, the evaluation of slurry dispersion phases has been performed using a variety of methods and tools. These include, for example, observing particle dispersion and measuring particle size and shape using a microscope; optical methods, such as observing particle size distribution using imaging, laser, and sensor technologies; and mechanical methods, such as quantifying slurry structure by measuring slurry viscosity.

[0009] However, optical methods are difficult to apply to opaque slurries and suffer from variations in quantification methods and equipment. Mechanical methods, however, offer limited information on slurry structure, resulting in a lack of correlation between slurry viscosity and actual dispersed phase-related issues, such as sedimentation, changes over time, filter clogging, and coating failure.

[0010] Therefore, there is an urgent need for the development of a technology for evaluating the slurry dispersion phase that enables rapid and accurate evaluation of changes in the slurry structure and can be applied to a wide range of slurries regardless of their properties, such as transparency or opacity.

[0011] The problem to be solved by the present invention is to provide a method for evaluating a slurry dispersion phase that can predict electrode fairness according to slurry composition in advance at the development stage, quickly evaluate changes in the structure of a slurry when fairness issues arise at the slurry manufacturing stage, and predict changes over time according to the slurry storage period in advance.

[0012] In addition, the present invention aims to provide a method for producing a slurry with improved reliability by using a method for evaluating the dispersion phase of the slurry.

[0013] However, the problems to be solved by the embodiments of the present invention are not limited to the problems described above and can be expanded in various ways within the scope of the technical ideas included in the present invention.

[0014] A slurry dispersion phase evaluation method according to one embodiment of the present invention measures the SMD value expressed by the following Equation 1 for the slurry:

[0015] [Formula 1]

[0016] SMD= G'1 / G'2

[0017] The above G'1 is the elastic modulus measured after stirring the slurry at a shear rate of 1000 / s, and the above G'2 is the elastic modulus measured after stirring the slurry at a shear rate of 10 / s.

[0018] In one embodiment, the slurry may include active material particles.

[0019] In one embodiment, the slurry may be stirred at a shear rate of 1000 / s to remove the flow history.

[0020] In one embodiment, each of the G'1 and the G'2 may be an elastic modulus measured by applying vibration of 0.1 Hz or more and 1 Hz or less in a stationary state after stirring the slurry at the shear rate.

[0021] In one embodiment, the vibration may be greater than or equal to 0.1 Hz and less than or equal to 0.5 Hz.

[0022] In one embodiment, the vibration may be 0.215 Hz.

[0023] In one embodiment, the vibration may be applied for a period of 10 seconds or more and 30 seconds or less.

[0024] In one embodiment, the larger the SMD value, the greater the dispersion instability of the slurry.

[0025] In one embodiment, if the SMD value is 0.1 or more and less than 5, the slurry dispersion phase can be judged to be good.

[0026] In one embodiment, if the SMD value is 5 or greater, the slurry dispersion phase may be judged to be defective.

[0027] A method for preparing a slurry according to one embodiment of the present invention comprises the steps of: preparing a slurry by mixing an active material, a binder, and optionally a conductive material in a solvent; and measuring an SMD value represented by the following Equation 1 for the slurry:

[0028] [Formula 1]

[0029] SMD= G'1 / G'2

[0030] The above G'1 is the elastic modulus measured after stirring the slurry at a shear rate of 1000 / s, and the above G'2 is the elastic modulus measured after stirring the slurry at a shear rate of 10 / s.

[0031] In one embodiment, if the SMD value is 0.1 or more and less than 5, the dispersion phase of the slurry is judged to be good, and a step of applying the slurry may be further included.

[0032] In one embodiment, if the SMD value is 5 or greater, the method may further include a step of determining that the dispersion phase of the slurry is defective and remanufacturing the slurry.

[0033] The slurry dispersion phase evaluation method of the present invention can predict electrode processability according to composition in advance at the slurry manufacturing stage.

[0034] Additionally, it is possible to predict in advance process quality issues such as coating defects, filter clogging, and mixing defects that may occur in the production line during the slurry manufacturing stage.

[0035] Additionally, it is possible to predict changes over time due to storage of the above slurry.

[0036] The slurry manufacturing method of the present invention can easily develop a slurry with improved stability by evaluating the dispersed phase of the manufactured slurry, and consequently improve product quality.

[0037] Figure 1 is a photograph evaluating the storage stability of slurry A.

[0038] Figure 2 is a photograph evaluating the storage stability of slurry C.

[0039] Figure 3 is a photograph evaluating the change over time of slurry B.

[0040] Figure 4 is a photograph evaluating the change over time of slurry C.

[0041] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0042] Additionally, throughout the specification, whenever a part is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0043] In this example, terms indicating directions such as front, back, left, right, up, and down are used, but these terms are only for convenience of explanation and may vary depending on the location of the target object or the location of the observer.

[0044] Furthermore, in this specification, “elastic modulus (G')” means bulk elastic modulus.

[0045]

[0046] A method for evaluating a dispersed phase of a slurry according to one embodiment of the present invention provides a method for measuring an SMD value expressed by the following equation 1 for a slurry.

[0047] [Formula 1]

[0048] SMD= G'1 / G'2

[0049] The inventors of the present application have confirmed that a slurry containing particles used as an organic-inorganic composite material exhibits thixotropy with sol-gel transition characteristics, and based on this characteristic, have developed an index capable of evaluating the dispersed phase of the slurry from the elastic modulus (G'). Specifically, the index is expressed as in Equation 1 above.

[0050] That is, the inventors of the present application measured the elastic modulus after stirring the slurry at a shear rate of 1000 / s to obtain the G'1 value, and measured the elastic modulus after stirring the slurry at a shear rate of 10 / s to obtain the G'2 value, and confirmed that as the value of (G'1 / G'2) increases, thixotropy increases, which increases the instability of the slurry dispersion phase due to flow and may cause problems in the actual process, thereby confirming that the SMD index represented by the above equation 1 can be an objective index.

[0051] This evaluation method can be applied to a slurry form of an organic-inorganic composite material, and is not limited thereto, specifically, the slurry can be applied to an electrode slurry containing active material particles, and more specifically, to an electrode slurry for a lithium secondary battery.

[0052] An electrode slurry of one embodiment can be prepared by mixing an active material, a binder, and optionally a conductive material in a solvent phase. The electrode slurry can be coated on a current collector and dried to form an electrode composite layer, thereby preparing a positive or negative electrode.

[0053] The active material may be a positive electrode active material or a negative electrode active material.

[0054] As a cathode active material, any compound known in the art that allows reversible intercalation and deintercalation of lithium may be used without limitation. Specifically, the cathode active material may be a lithium composite metal oxide containing lithium and one or more metals, such as cobalt, manganese, nickel, or aluminum.

[0055] Lithium composite metal oxides include lithium-manganese oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt oxides (e.g., LiCoO2, etc.), lithium-nickel oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese oxides (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 r1 )O2(wherein, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Nip1 Co q1 Mn r2 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2) etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 )O2 (wherein, M is at least one selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are atomic fractions of independent elements, such that 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1), etc.), and any one or two or more compounds thereof may be included.

[0056] Binders are used to bind the active material and conductive material and to bind them to the current collector. Non-limiting examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethacrylic acid (PMA), polymethyl methacrylate (PMMA), polyacrylamide (PAM), polymethacrylamide, polyacrylonitrile (PAN), polymethacrylonitrile, polyimide (PI), alginic acid, alginate, chitosan, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluoroelastomer, and various copolymers thereof. The above binder may be included in an amount of 1 wt% to 30 wt%, specifically 1 wt% to 10 wt%, and more specifically 1 wt% to 5 wt%, based on the total weight of the slurry.

[0057] Conductive agents are used to further improve the conductivity of electrode active materials. The conductive agent is not particularly limited as long as it has electrical conductivity and does not cause chemical changes in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorinated carbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and polyphenylene derivatives may be used. The conductive agent may be included in an amount of 1 wt% to 30 wt%, specifically 1 wt% to 10 wt%, and more specifically 1 wt% to 5 wt%, based on the total weight of the slurry.

[0058] The solvent may be, in general, an organic solvent or an aqueous solvent, and for example, as the organic solvent, one or a mixture of two or more selected from the group consisting of N-methyl-2-pyrrolidone (NMP), methoxy propyl acetate, butyl acetate, glycol acid, butyl ester, butyl glycol, methylalkylpolysiloxane, alkylbenzene, propylene glycol, xylene, monophenyl glycol, aralkyl-modified methylalkylpolysiloxane, polyether-modified dimethylpolysiloxane copolymer, polyether-modified dimethylpolysiloxane copolymer, polyacrylate solution, alkylbenzene, diisobutyl ketone, organic-modified polysiloxane, butanol, isobutanol, modified polyacrylate, modified polyurethane, and polysiloxane-modified polymer may be preferably used.

[0059] Additionally, water can be used as an aqueous solvent.

[0060]

[0061] Hereinafter, a method for evaluating a slurry dispersion phase by measuring the SMD value represented by the above formula 1 is described.

[0062] In the above equation 1, G'1 is the elastic modulus measured after stirring the slurry at a shear rate of 1000 / s. Specifically, it is the elastic modulus measured after stirring the slurry at a shear rate of 1000 / s and applying vibration of 0.1 Hz or more and 1 Hz or less to the slurry while the slurry is stationary.

[0063] In the above equation 1, G'2 is the elastic modulus measured after stirring the slurry at a shear rate of 10 / s. Specifically, it is the elastic modulus measured after stirring the slurry at a shear rate of 10 / s and applying vibration of 0.1 Hz or more and 1 Hz or less to the slurry while the slurry is stationary.

[0064] The stirring of the above slurry may be performed for 30 seconds or more at each shear rate, for example, 60 seconds. If stirring is performed for less than 30 seconds, the slurry may not reach a steady state, or the operation / measurement reliability of the equipment may deteriorate.

[0065] The above stirring is not limited to any method capable of stirring a slurry having thixotropic properties, but may be performed, for example, using a rheometer device, and more specifically, using a Couette cell of a rheometer.

[0066] After stirring the slurry under the conditions described above, vibration is applied while the slurry is stationary and the elastic modulus is measured. For example, the elastic modulus can be measured through an oscillatory frequency sweep test.

[0067] At this time, the vibration applied to the slurry may be within the range of 0.1 Hz or more and 1 Hz or less. Applying vibration below 0.1 Hz, outside the above range, may increase the measurement error of the device, thereby reducing reliability. Furthermore, applying vibration exceeding 1 Hz may potentially destroy the slurry structure, which is undesirable.

[0068] Therefore, the frequency at which the slurry structure change is the greatest in the above range can be selected, and the elastic modulus (G') values ​​at this specific frequency can be set as the target for introduction into Equation 1.

[0069] According to the inventors of the present application, the selection of such values ​​is not limited and may be affected by the composition of the target slurry being measured, but in general, it has been confirmed that a greater change is exhibited at lower Hz values. For example, the vibration applied to the slurry may be specifically 0.1 Hz or more and 0.5 Hz or less, more specifically 0.1 Hz or more and 0.3 Hz or less, and most specifically 0.215 Hz.

[0070] At this time, the vibration may be applied for 10 seconds or more and 30 seconds or less, specifically 10 seconds or more and 20 seconds or less, and even more specifically 10 seconds or more and 15 seconds or less.

[0071] In addition, the elastic modulus of the above slurry can be measured for a slurry in the range of 20 degrees Celsius or more and 30 degrees Celsius or less, and for example, can be measured for a slurry at 23 degrees Celsius.

[0072] The elastic modulus of the above slurry can be affected by temperature, and therefore, it is preferable to measure the slurry at the same temperature. At this time, if the temperature is too high, the slurry's viscosity decreases, and if it is too low, the viscosity increases. Therefore, room temperature (23 degrees Celsius), which is the temperature at which the slurry is actually used in the process, may be preferable.

[0073] The G'1 and G'2 values ​​can be obtained for the elastic modulus measured as above, and the SMD value can be obtained by substituting them into Equation 1.

[0074] Meanwhile, in order to improve measurement precision and reproducibility, the slurry evaluation method of the present invention removes and initializes the flow history by stirring the slurry before measuring the elastic modulus.

[0075] At this time, the stirring for the initialization may be performed for 30 seconds to 100 seconds at a shear rate of 500 / s to 1000 / s, and more specifically, may be performed for 50 seconds to 80 seconds at a shear rate of 1000 / s to 1500 / s. For example, it may be performed for 60 seconds at a shear rate of 1000 / s.

[0076] Outside the above range, if stirring is performed at too low a speed or for too short a time, initialization such as removal of flow history may not be performed properly, and stirring at too high a speed or for too long a time makes uniform stirring difficult and may cause a slip phenomenon, which is not desirable.

[0077] The above stirring is not limited to a device that stirs a slurry having the same thixotropic properties as described above, but may be performed, for example, through a rheometer device, and more specifically, may be performed using a Couette cell of a rheometer.

[0078] It is judged that the larger the SMD value of the above equation 1 obtained through this process, the greater the instability of the slurry dispersion phase. Specifically, if the SMD value is 0.1 or more and less than 5, the slurry dispersion phase can be judged to be good. In addition, if the SMD value is 5 or more, the slurry dispersion phase can be judged to be poor. If the slurry dispersion phase is judged to be good, the slurry can be expected to have excellent reliability. If the slurry dispersion phase is judged to be poor, the slurry can be expected to cause problems such as slurry sedimentation, change over time, and filter clogging when applied to an actual process.

[0079] Therefore, through the above slurry evaluation method, it is possible to predict fairness issues according to composition and mixing conditions from the slurry manufacturing stage and production line in advance, derive appropriate composition and mixing conditions, and also review the appropriateness of slurry storage, etc.

[0080] In addition, this method is not limited to optical properties, and according to the results of review by the inventors of the present application, it has been confirmed that the information obtained therefrom has an effect on changes over time, sedimentation, etc. that appear in an actual slurry, and thus the dispersed phase of the slurry can be accurately evaluated.

[0081]

[0082] A method for manufacturing a slurry according to one embodiment of the present invention can utilize the slurry dispersion phase evaluation method described above.

[0083]

[0084] The slurry manufacturing method of the present invention comprises:

[0085] A step of preparing a slurry by mixing an active material, a binder, and optionally a conductive material in a solvent phase; and

[0086] A step of measuring the SMD value represented by the following equation 1 for the above slurry; comprising:

[0087] [Formula 1]

[0088] SMD= G'1 / G'2

[0089] The above G'1 is the elastic modulus measured after stirring the slurry at a shear rate of 1000 / s,

[0090] The above G'2 is the elastic modulus measured after stirring the slurry at a shear rate of 10 / s.

[0091]

[0092] In one embodiment, the slurry is an electrode slurry, and the step of preparing the slurry is a step of mixing an active material, a binder, and optionally a conductive material in a solvent phase. The above-described content applies equally to each component of the slurry, and a detailed description thereof is omitted.

[0093] The step of measuring the SMD value is a step of measuring the SMD value expressed by the following equation 1 for the manufactured slurry.

[0094] [Formula 1]

[0095] SMD= G'1 / G'2

[0096] The above G'1 is the elastic modulus measured after stirring the slurry at a shear rate of 1000 / s,

[0097] The above G'2 is the elastic modulus measured after stirring the slurry at a shear rate of 10 / s.

[0098] The specific explanation for Equation 1 applies equally to the above.

[0099]

[0100] Meanwhile, a method for preparing a slurry of one embodiment includes a step of preparing a slurry and a step of measuring an SMD value for the prepared slurry, and may further include the following steps.

[0101] In one embodiment, the slurry manufacturing method may further include a step of applying the manufactured slurry, judging that the dispersion phase of the slurry is good when the measured SMD value is 0.1 or more and less than 5. The slurry may be applied to a current collector to coat it, and then subjected to a drying and rolling process to manufacture an electrode.

[0102] Alternatively, the slurry manufacturing method of one embodiment may further include a step of determining that the dispersion phase of the slurry is defective when the measured SMD value is 5 or higher, and remanufacturing the slurry. For example, a defect in the dispersion phase of the slurry may occur due to the mixing of moisture or foreign substances during the slurry manufacturing process. Alternatively, a defect in the dispersion phase may occur due to an error in mixing each component by weight during the slurry manufacturing process. The present invention can measure the SMD of the manufactured slurry, and then predict a defect in the dispersion phase of the slurry in advance based on the SMD value.

[0103]

[0104] As described above, the slurry manufacturing method of one embodiment includes a step of manufacturing a slurry and a step of measuring the SMD value of the manufactured slurry, thereby enabling the dispersion phase of the slurry to be predicted in advance before proceeding with the process and minimizing process defects.

[0105] Accordingly, the present invention can provide a method for producing a slurry with improved reliability, facilitate the development of a slurry with improved stability, and consequently improve product quality.

[0106]

[0107] Example

[0108] Hereinafter, with reference to examples and comparative examples, it is explained that the evaluation method of the present invention and the index expressed by the above formula 1 have a reliable correlation with the slurry stability that appears in an actual process, such as sedimentation, change over time, filter clogging, etc.

[0109]

[0110] <Example 1: Preparation of slurry A>

[0111] Active material (Li(Ni) 1 / 3 Co 1 / 3 Mn 1 / 3)O2)), a conductive agent (carbon nanotube), and a binder (polyvinylidene fluoride) were mixed in a weight ratio of 96.4:1.8:1.8 in an NMP solvent to a solid concentration of 75%.

[0112]

[0113] <Example 2: Preparation of slurry B>

[0114] Active material (Li(Ni) 1 / 3 Co 1 / 3 Mn 1 / 3) O2)), a conductive agent (carbon black), and a binder (polyvinylidene fluoride) were mixed in a weight ratio of 96.4:1.8:1.8 in an NMP solvent to a solid concentration of 75%.

[0115]

[0116] <Comparative Example 1: Preparation of Slurry C>

[0117] Active material (LFP), conductive material (carbon nanotube), and binder (polyvinylidene fluoride) were mixed in a weight ratio of 96.4:1.8:1.8 in NMP solvent to a solid concentration of 60%.

[0118]

[0119] Experimental Example 1

[0120] The following process was performed on the above slurry A to measure G'1.

[0121] First, slurry A at room temperature (23 degrees Celsius) was placed in the Couette cell of a rheometer and stirred at a shear rate of 1000 / s for 60 seconds to remove the flow history of the slurry.

[0122] Afterwards, the slurry A was stirred at a shear rate of 1000 / s for 60 seconds, and then an oscillatory frequency sweep test was performed while applying vibration of 0.215 Hz in a stationary state. However, before applying the vibration of 0.215 Hz, in order to determine the frequency value that exhibits the greatest characteristic change in the slurry structure, various vibration frequencies were applied within the range of 0.1 Hz or more and 1 Hz or less for 15 seconds and the elastic modulus value was measured.

[0123] Here, for the above test, the shear rate was set to 1000 / s, the amplitude (Strain) to 0.5%, and the frequency to 0.1-1 Hz.

[0124] The same process as above was performed on slurry B and slurry C, and G'1 of each was measured.

[0125]

[0126] Experimental Example 2

[0127] The following process was performed on the above slurry A to measure G'2.

[0128] First, slurry A at room temperature (23 degrees Celsius) was placed in the Couette cell of a rheometer and stirred at a shear rate of 1000 / s for 60 seconds to remove the flow history of the slurry.

[0129] Afterwards, the slurry A was stirred at a shear rate of 10 / s for 60 seconds, and then an oscillatory frequency sweep test was performed while applying vibration of 0.215 Hz in a stationary state as in Experimental Example 1.

[0130] Here, for the above test, the shear rate was set to 10 / s, the amplitude (Strain): 0.5%, and the frequency: 0.1-1Hz.

[0131] The same process was performed on slurry B and slurry C to measure their respective G'2.

[0132] The elastic modulus values ​​measured in Experimental Examples 1 and 2 are shown in Table 1 below.

[0133] Shear rate Slurry A Slurry B Slurry C 10 / s 7.4800.9362.1141000 / s 7.6832.23715.770

[0134] Experimental Example 3

[0135] Referring to Table 1 and Equation 1 above, the SMD values ​​of slurry A, slurry B, and slurry C were measured and shown in Table 2 below. In Table 2 above, the SMD values ​​are rounded to the third decimal place.

[0136] Slurry A Slurry B Slurry CSMD (@ 0.215Hz) 1.022.397.46

[0137] Referring to Table 2 above, slurries A and B having an SMD value of less than 5 were judged to have good slurry dispersions. Slurry C having an SMD value of more than 5 was judged to have poor slurry dispersions, i.e., it can be predicted to have high structural instability.

[0138] Experimental Example 4

[0139] In order to confirm the storage stability of the slurries A and C manufactured above, each slurry at room temperature (23 degrees Celsius) was poured into a glass substrate, left in an environment of 23 degrees Celsius for 7 days, and then the occurrence of sediment was confirmed, and the results are shown in Figures 1 and 2 below.

[0140] Referring to Fig. 1, it can be seen that slurry A does not produce sediment, while referring to Fig. 2, slurry C produces a large amount of sediment.

[0141]

[0142] Experimental Example 5

[0143] In order to check the filter clogging for the slurries B and C manufactured above, when slurries B and C at room temperature (23 degrees Celsius) were each injected into a 150 mesh filter, the pressure applied to the filter over time was measured using a pressure sensor.

[0144] The measurement results showed that slurry B showed a gradual increase in pressure over time, whereas slurry C showed a rapid increase in pressure from the beginning. In other words, it was expected that filter clogging would occur when slurry C was used.

[0145]

[0146] Experimental Example 6

[0147] In order to check the change over time for the slurries A and C manufactured above, 100 ml of each slurry at room temperature (23 degrees Celsius) was poured onto a glass substrate and left in an environment of 23 degrees Celsius for 5 days, and the results are shown in Figures 3 and 4 below.

[0148] Referring to Fig. 3, it can be seen that slurry B maintains a slurry state, while referring to Fig. 4, slurry C hardens and changes into a phase close to a solid state.

[0149]

[0150] Examining the above Experimental Examples 3 to 6, the evaluation method according to the present invention was used to determine the good / bad dispersion of the slurry, and the results of sedimentation evaluation, filter clogging evaluation, and time-dependent change evaluation were obtained. Therefore, it can be confirmed that the slurry dispersion evaluation method according to the present invention can serve as an indicator of the dispersion of an actual slurry.

[0151]

[0152] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. Slurry dispersion phase evaluation method for measuring the SMD value expressed by the following equation 1 for the slurry: [Formula 1] SMD= G'1 / G'2 The above G'1 is the elastic modulus measured after stirring the slurry at a shear rate of 1000 / s, The above G'2 is the elastic modulus measured after stirring the slurry at a shear rate of 10 / s.

2. In paragraph 1, The above slurry is a method for evaluating a slurry dispersion phase containing active material particles.

3. In paragraph 1, The above slurry is a slurry dispersion phase evaluation method in which the flow history is removed by stirring at a shear rate of 1000 / s.

4. In paragraph 1, The above G'1 and the above G'2 are each elastic moduli measured by stirring the slurry at the above shear rate and then applying vibration of 0.1 Hz or more and 1 Hz or less in a stationary state, and a method for evaluating a slurry dispersion phase.

5. In paragraph 4, The above vibration is a method for evaluating a slurry dispersion phase of 0.1 Hz or more and 0.5 Hz or less.

6. In paragraph 4, The above vibration is a slurry dispersion phase evaluation method of 0.215 Hz.

7. In paragraph 4, The above vibration is a method for evaluating a slurry dispersion phase applied for 10 seconds or more and 30 seconds or less.

8. In paragraph 1, A method for evaluating a slurry dispersed phase, wherein the larger the SMD value, the greater the dispersed phase instability of the slurry.

9. In paragraph 1, A slurry dispersion phase evaluation method in which the slurry dispersion phase is judged to be good when the above SMD value is 0.1 or more and less than 5.

10. In paragraph 1, A slurry dispersion phase evaluation method in which the slurry dispersion phase is judged to be defective when the above SMD value is 5 or higher.

11. A step of preparing a slurry by mixing an active material, a binder, and optionally a conductive material in a solvent; and A method for manufacturing a slurry, comprising: a step of measuring an SMD value represented by the following formula 1 for the above slurry; [Formula 1] SMD= G'1 / G'2 The above G'1 is the elastic modulus measured after stirring the slurry at a shear rate of 1000 / s, The above G'2 is the elastic modulus measured after stirring the slurry at a shear rate of 10 / s.

12. In paragraph 11, A slurry manufacturing method further comprising a step of applying the slurry, wherein the dispersion phase of the slurry is judged to be good when the SMD value is 0.1 or more and less than 5.

13. In paragraph 11, A slurry manufacturing method further comprising a step of remanufacturing the slurry, determining that the dispersion phase of the slurry is defective when the SMD value is 5 or more.

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