[One]Cross Citation with Related Applications
[2]This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0026479, filed on March 07, 2019 and Korean Patent Application No. 10-2019-0027180, filed on March 08, 2019, All contents disclosed in the literature of the Korean patent application are incorporated as a part of this specification.
[3]
[4]
technical field
[5]
The invention upon XRD measurement, and La (100) is less than 7.0nm, a specific surface area of 100m 2 / g to 196m 2 the invention relates to an electrode and a secondary battery comprising the carbon nanotubes, the carbon nanotubes / g.
background
[6]
Recently, as technology development and demand for mobile devices increase, the demand for batteries as an energy source is rapidly increasing, and accordingly, various researches on batteries capable of meeting various needs are being conducted. In particular, as a power source for such a device, a lithium secondary battery having a high energy density and excellent lifespan and cycle characteristics is being actively researched.
[7]
A lithium secondary battery includes a positive electrode including a positive electrode active material capable of insertion/desorption of lithium ions, a negative electrode including a negative electrode active material capable of insertion/deintercalation of lithium ions, and an electrode having a microporous separator interposed between the positive electrode and the negative electrode It means a battery in which a non-aqueous electrolyte containing lithium ions is included in the assembly.
[8]
The anode and/or the cathode may include a conductive material to improve conductivity. Conventionally, point-type conductive materials such as carbon black have been mainly used, and in order to further improve conductivity, linear conductive materials such as carbon nanotubes and carbon nanofibers and planar conductive materials such as graphene are also used.
[9]
In the case of the graphene, there is an advantage of excellent electrical conductivity. However, it is advantageous to form graphene as a single layer in order to improve conductivity, but the manufacturing price increases because the process for manufacturing in the form of a single layer is very difficult. Conversely, when graphene has a thickness greater than or equal to an appropriate level, there is a problem in that the effect of improving electrical conductivity is insufficient. In addition, even when graphene itself having an appropriate level of thickness of 10 nm or less is used as a conductive material, the performance of the battery is deteriorated, such as an increase in electrode resistance because the graphene cannot easily move to the electrolyte within the electrode due to excessive surface contact of the graphene. is lowered
[10]
On the other hand, in the case of the conventional carbon nanotube corresponding to the linear conductive material, the electrical conductivity is excellent, but the crystallinity is too high, so the flexibility is low, and it is stiff, and the carbon nanotube along the surface of the active material particle. are difficult to adhere smoothly and are randomly and linearly arranged in a three-dimensional space. Accordingly, the probability that the carbon nanotubes and the active material particles are interconnected decreases. Accordingly, a contact point or area between the active material particles and the carbon nanotube is reduced, making it difficult to secure a conductive path, and there is a problem in that the resistance of the battery increases. In addition, in the case of the existing carbon nanotubes, it is difficult to be smoothly dispersed in the slurry for forming the electrode, the resistance in the electrode is not uniform, and there are problems in that the lifespan characteristics of the battery are deteriorated.
[11]
Conventionally, in order to solve the problem of carbon nanotubes, a method of controlling the viscosity of a conductive material dispersion in which carbon nanotubes are previously dispersed or the type of dispersant included in the conductive material dispersion has been used. However, since such a method does not change the physical properties of the carbon nanotube itself, there is a limit in solving the above-mentioned problems.
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[12]
One problem to be solved by the present invention is a carbon nanotube capable of smoothly adhering to active material particles and uniformly dispersed in an electrode, thereby lowering the resistance of the battery and improving the lifespan characteristics of the battery, the carbon nanotube It is to provide an electrode and a secondary battery comprising a.
means of solving the problem
[13]
According to an embodiment of the present invention, in XRD measurement , a carbon nanotube having a La(100) of less than 7.0 nm and a specific surface area of ​​100 m 2 /g to 196 m 2 /g is provided.
[14]
According to another embodiment of the present invention, an electrode including the carbon nanotube is provided.
[15]
According to another embodiment of the present invention, a secondary battery including the electrode is provided.
Effects of the Invention
[16]
According to the present invention, La(100) of carbon nanotubes is less than 7.0 nm. That is, the carbon nanotubes have short growth units (between nodes) and have low crystallinity, and thus have high flexibility compared to conventional carbon nanotubes. Accordingly, the active material particles and the carbon nanotubes may be in close contact with each other, so that the contact area may be increased, and thus the battery resistance may be reduced. In addition, since the specific surface area of ​​the carbon nanotubes is as low as 100 m 2 /g to 196 m 2 /g level, side reactions with the electrolyte can be minimized, the dispersion in the electrode is smooth, and even when the carbon nanotubes are used in a small amount A conductive network in the electrode can be efficiently formed. Furthermore, the surface of the carbon nanotubes has many defects, and since the carbon nanotubes contain a high content of oxygen-containing functional groups, the carbon nanotubes can be uniformly dispersed in the electrode slurry. Accordingly, the lifespan characteristics of the manufactured battery may be improved.
Brief description of the drawing
[17]
1 is a schematic view of Lc values ​​and La values ​​indicating crystallinity in the vertical and horizontal directions with respect to the growth axis of the carbon nanotube (FIG. 1 (a)), and a TEM photograph of the carbon nanotube of the present invention (FIG. 1 (b)), and a TEM photograph of a conventional carbon nanotube (FIG. 1 (c)).
[18]
2 is a TEM photograph of the carbon nanotube of Example 1 before graphitization at 2500 ° C (FIG. 2 (a), (b)) and a TEM photograph of the carbon nanotube of Example 1 that was graphitized ( 2 (c), (d)).
[19]
3 is a TEM photograph of the carbon nanotube of Comparative Example 1 before graphitization at 2500° C. (FIG. 3 (a), (b)) and a TEM photograph of the carbon nanotube of Comparative Example 1 subjected to the graphitization treatment ( 3 (c), (d)).
Modes for carrying out the invention
[20]
Hereinafter, the present invention will be described in more detail to help the understanding of the present invention.
[21]
The terms or words used in the present specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention.
[22]
The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise.
[23]
In the present specification, terms such as "comprise", "comprising" or "have" are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but one or more other features or It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, elements, or combinations thereof.
[24]
In the present invention, the carbon nanotube has a graphite sheet having a cylindrical shape with a nano-size diameter, and has an sp 2 bonding structure. In this case, the characteristics of a conductor or a semiconductor may be exhibited according to the angle and structure at which the graphite surface is rolled.
[25]
In the present specification, La(100) and Lc(002) may be measured by X-ray diffraction analysis (XRD). Specifically, XRD analysis can use Bruker AXS D4 Endeavor XRD (voltage: 40 kV, current: 40 mA), Cu Ka radiation (wavelength: 1.54 Å, 2-Theta every 0.02° from 10° to 90° It can be measured at a scanning speed of 87.5 seconds. The half width of the appearing (100) crystal peak can be measured, and Lc(002) and La(100) values ​​can be obtained by calculating it using the Scherrer equation.
[26]
A D /A G (ratio) of the present specification can be measured from the wavelength-peak graph during Raman spectrum measurement. Specifically, after adjusting the graph by setting a base line so that the D peak and the G peak can be distinguished, the graph area (A D ) of the part where the D peak appears is the graph area of the part where the G peak appears ( A G ) (using built-in software, NRS-2000B, Jasco). In the Raman spectrum, 1590cm -1 G peak in the neighborhood of the carbon sp 2 E of the coupling 2g will resulting from vibration modes, 1350cm -1 D is a peak in the vicinity of the carbon sp 2 appears when there is a defect in the coupling.
[27]
In the present specification, the specific surface area of ​​carbon nanotubes was measured by the BET method, and specifically, the amount of nitrogen gas adsorbed under liquid nitrogen temperature (77 K) was calculated using BELSORP-mini II manufactured by BEL Japan.
[28]
In the present specification, the content (weight %) of the oxygen atom-containing functional group in the carbon nanotube was measured by elemental analysis using ONH836 Analyzer of LECO.
[29]
[30]

[31]
[32]
In the carbon nanotube according to an embodiment of the present invention, when measured by XRD, La(100) may be less than 7.0 nm, and a specific surface area may be 100 m 2 /g to 196 m 2 /g.
[33]
[34]
When carbon nanotubes are produced, a) gradient change in the concentration of hydrocarbon gas up to the catalyst, b) solubility of carbon atoms and diffusivity in the catalyst according to the pseudo-melting state of the catalyst, c) from the catalyst There are variables such as temperature change during growth in which carbon atoms are arranged (exothermic reaction when hydrocarbon gas is decomposed on the catalyst and endothermic reaction when carbon nanotubes grow due to rearrangement of carbon atoms in the catalyst, etc.). Since the above parameters change little by little during carbon nanotube production, in general, it is difficult for carbon nanotubes to continuously grow without defects along the growth direction (longitudinal direction to long-axis direction) during carbon nanotube growth, and instantaneous changes in parameters Accordingly, it inevitably has a period of quiescence. Accordingly, a carbon nanotube having nodes like a bamboo-like is formed, and the length between the nodes (growth units) corresponds to the growth unit length of the carbon nanotube. In this case, the La(100) is a parameter in which the length of the growth unit and the crystallinity of the growth unit are reflected (refer to (a) of FIG. 1).
[35]
In the present invention, a fluidized bed reactor with a large gas flow change and a large reaction temperature gradient (change) is used, in particular, a very large fluidized bed reactor, and carbon nanotubes are manufactured at a relatively low temperature, so continuous growth is intentionally A carbon nanotube having a short growth unit length and low crystallinity of the growth unit can be obtained.
[36]
[37]
The carbon nanotubes may have a La(100) of less than 7.0 nm when measured by XRD, specifically, 5.00 nm or more and less than 7.0 nm, and more specifically, 5.00 nm to 6.98 nm. Unlike the form having no nodes or a long growth unit length (a form close to a straight line, see Fig. 1 (c)), the carbon nanotube has a short growth unit length and includes a plurality of nodes, so it has high flexibility. It can be (see Fig. 1 (b)). Accordingly, since the surface of the active material particles and the carbon nanotubes can more smoothly adhere to each other in the electrode, the resistance in the electrode can be reduced. Preferably, the La(100) may be 5.00 nm to 6.82 nm.
[38]
[39]
When carbon nanotubes are graphitized at 2500° C., the crystallinity of parts having low crystallinity is increased, and the curved shape is changed to a straight shape due to the low crystallinity. At this time, the carbon nanotube structures on both sides of the node are not interconnected due to the presence of the node.
[40]
In the case of a conventional carbon nanotube having a tubular highly crystalline sp2 structure, since there are few defects between nodes, La(100) does not significantly increase even if graphitization treatment is performed at a level of 2500°C. On the other hand, since the carbon nanotube of the present invention has low crystallinity and a short growth unit structure, defects causing low crystallinity are eliminated during graphitization (defects causing low crystallinity between nodes) However, as the curved shape is changed to a straight shape during graphitization treatment), the La(100) value increases, and this increase is larger than the conventional carbon nanotubes having high crystallinity and long growth units. good In addition, since the carbon nanotubes of the present invention have short growth units, La(100) values ​​before and after the graphitization treatment are both at a small level compared to the conventional carbon nanotubes having high crystallinity and long growth units.
[41]
[42]
The carbon nanotube of the present invention has the following characteristics. In the carbon nanotube, BA may be 0.70 nm or more, specifically 0.70 nm to 2.00 nm. Here, A is La (100) (unit: nm) in XRD measurement of the carbon nanotube of the present invention before graphitization at 2500° C., and B is the graphitized carbon nanotube. In XRD measurement, it is La(100) (unit: nm). The time of the graphitization treatment may be 10 minutes or more. When the carbon nanotube is graphitized at a high temperature of 2500° C. or higher (in this specification, it is treated at 2500° C. to check the BA value), the crystallinity of the carbon nanotube reaches a maximum. In the case of the conventional carbon nanotube, the BA is less than 0.70 nm, which means that the conventional carbon nanotube has high crystallinity before the graphitization treatment. That is, since the conventional carbon nanotube has low flexibility due to high crystallinity, it is difficult for the active material particles and the carbon nanotube to adhere to each other, thereby increasing the resistance of the battery. Conversely, the BA of 0.70 nm or more means that the carbon nanotubes of this embodiment before graphitization have low crystallinity (crystallinity within a growth unit) and high flexibility. Accordingly, the active material particles and the carbon nanotubes may be in close contact with each other in the electrode. Accordingly, the resistance of the battery can be reduced. More specifically, the BA may be 0.80 nm to 2.00 nm.
[43]
[44]
In the carbon nanotube, DC may be 0.18 nm or less, specifically 0 nm to 0.15 nm, and more specifically 0 nm to 0.1 nm. Here, C is Lc (002) (unit: nm) when XRD measurement of the carbon nanotube before graphitization at 2500° C., and D is XRD measurement of the graphitized carbon nanotube hour, Lc(002) (unit: nm). The time of the graphitization treatment may be 10 minutes or more. Lc(002) of the carbon nanotube is a parameter corresponding to the thickness of a carbon layer composed of a plurality of walls in the multi-wall carbon nanotube. That is, the DC means a change in the thickness of the carbon layer. In the case of the conventional carbon nanotube, the crystallinity in the growth direction is high, but the crystallinity in the thickness direction of the carbon layer is low, so that DC exceeds 0.18 nm. This may be due to impurities present on the surface of the carbon nanotubes. The impurity is an amorphous carbon material produced by incomplete combustion of hydrocarbon gas on the surface of the carbon nanotube (refer to FIG. impurity of When the impurity is present in a significant amount, the DC shows a high value. The impurities are electrochemically CO, CO 2 , or CH 4It causes side reactions that cause gases, such as, and degrades the performance of the battery. Conversely, the DC of 0.18 nm or less means that the amount of impurities on the surface of the carbon nanotubes of this embodiment before the graphitization treatment is remarkably small and the purity of the carbon nanotubes is high. Accordingly, the occurrence of the unnecessary side reaction may be suppressed, and thus the performance of the battery may be improved.
[45]
[46]
When measuring a Raman spectrum for the carbon nanotube, A D /A G may be 0.9 or more, specifically, may be 0.9 to 2.0. When the above range is satisfied, it means that the carbon nanotube of this embodiment has low crystallinity and high flexibility. Accordingly, the active material particles and the carbon nanotubes may be in close contact with each other in the electrode. Accordingly, the resistance of the battery can be reduced.
[47]
More specifically, A D /A G may be 0.92 to 0.96. In this case, since the carbon nanotubes have low crystallinity and few defects that cause unnecessary side reactions, side reactions that cause gases such as CO, CO 2 , or CH 4 are suppressed, so that the performance of the battery can be further improved. .
[48]
[49]
In the carbon nanotube, EF may be 0.50 or more, specifically 0.50 to 1.0. E is when the Raman spectrum is measured for the carbon nanotube before graphitization at 2500° C., A D /A G , and F is when the Raman spectrum is measured for the graphitized carbon nanotube, A D / a G a. The time of the graphitization treatment may be 10 minutes or more. When the carbon nanotubes are graphitized at 2500° C., the crystallinity of the carbon nanotubes reaches a maximum. In the case of the conventional carbon nanotube, the EF is less than 0.50, which means that the conventional carbon nanotube has high crystallinity before the graphitization treatment. That is, since the conventional carbon nanotube has low flexibility due to high crystallinity, it is difficult for the active material particles and the carbon nanotube to adhere to each other, thereby increasing the resistance of the battery. Conversely, EF of 0.50 or more means that the carbon nanotubes of this embodiment before graphitization have low crystallinity and high flexibility. Accordingly, the active material particles and the carbon nanotubes may be in close contact with each other in the electrode. Accordingly, the resistance of the battery can be reduced. More specifically, the EF may be 0.5 to 0.58. In this case, since the crystallinity of the carbon nanotube is low and there are few defects that cause unnecessary side reactions, CO, CO 2, or a side reaction that causes a gas such as CH 4 may be suppressed to further improve the performance of the battery.
[50]
[51]
In the carbon nanotube, a Raman spectrum measurement, G peak (1590cm -1 The half-value width of a peak near) 60cm -1 it can be at least, specifically 60cm -1 to 150cm -1 may be. The half width corresponds to the crystallinity of the carbon nanotube. That is, in the case of the conventional carbon nanotube, since the half width is less than 60 cm -1 , it has high crystallinity, and thus the carbon nanotube has low flexibility. On the other hand, in the case of the carbon nanotube of this embodiment, since the half width is 60 cm -1 or more, it means that it has low crystallinity and high flexibility. Accordingly, the active material particles and the carbon nanotubes may be in close contact with each other in the electrode. Accordingly, the resistance of the battery can be reduced.
[52]
More specifically, the half width may be 65 cm -1 to 100 cm -1 . In this case, since the carbon nanotubes have low crystallinity and few defects that cause unnecessary side reactions, side reactions that cause gases such as CO, CO 2 , or CH 4 are suppressed, so that the performance of the battery can be further improved. .
[53]
[54]
In the carbon nanotube, GH may be 15 cm -1 or more, specifically 15 cm -1 to 100 cm -1 may be. G is the half-width of the G peak (unit: cm -1 ) when measuring the Raman spectrum of the carbon nanotube before graphitization at 2500° C. , and H is the graphitized carbon nanotube with respect to the carbon nanotube. When measuring a Raman spectrum, it is the full width at half maximum of the G peak (unit: cm -1 ). In the case of the conventional carbon nanotube, the GH is less than 15 cm -1 , which means that the conventional carbon nanotube has high crystallinity before the graphitization treatment. That is, since the conventional carbon nanotube has low flexibility due to high crystallinity, it is difficult for the active material particles and the carbon nanotube to adhere to each other, thereby increasing the resistance of the battery. Conversely, if the GH is 15 cm -1 or more, it means that the carbon nanotubes of this embodiment before graphitization have low crystallinity and high flexibility. Accordingly, the active material particles and the carbon nanotubes may be in close contact with each other in the electrode. Accordingly, the resistance of the battery can be reduced.
[55]
More specifically, the GH may be 20cm -1 to 30cm -1 . In this case, since the carbon nanotubes have low crystallinity and few defects that cause unnecessary side reactions, side reactions that cause gases such as CO, CO 2 , or CH 4 are suppressed, so that the performance of the battery can be further improved. .
[56]
[57]
The specific surface area of ​​the carbon nanotubes may be 100m 2 /g to 196m 2 /g, specifically 150m 2 /g to 185m 2 /g. When the specific surface area is satisfied, the side reaction with the electrolyte can be minimized, the dispersion in the electrode is smooth, the conductive network in the electrode can be efficiently formed even when the carbon nanotubes are used in a small amount, and the content of the binder is reduced can do it The specific surface area is lower than that of general carbon nanotubes, and this may be a result derived through control of the supported catalyst preparation conditions, etc.
[58]
[59]
The carbon nanotube may include a functional group containing an oxygen atom. Specifically, the functional group may include at least one selected from the group consisting of a carbonyl group, a carboxyl group, and a hydroxyl group.
[60]
The functional group containing the oxygen atom may be included in the carbon nanotube in an amount of 1.2 wt% or more, specifically, in an amount of 1.5 wt% to 5.0 wt%. The content range of the functional group is derived by the manufacturing method introduced in the present invention, and is not subjected to separate oxygen treatment after carbon nanotubes are manufactured. When the above range is satisfied, since the carbon nanotubes can be smoothly dispersed in the conductive material dispersion (carbon nanotube dispersion) and the electrode slurry, the powder resistance of the electrode slurry is lowered, and the lifespan characteristics of the battery can be improved.
[61]
More specifically, the functional group containing the oxygen atom may be included in the carbon nanotube in an amount of 1.7 wt% to 3.0 wt%. In this case, the performance of the battery may be improved based on the excellent electrical conductivity of the carbon nanotubes while smooth dispersion is possible as described above.
[62]
[63]
The carbon nanotubes may be multi-walled carbon nanotubes. When the carbon nanotube is a multi-walled carbon nanotube, it has the aforementioned growth unit length even with a low-cost process, and has excellent conductivity and flexibility, and can be smoothly dispersed in the electrode. On the other hand, in the case of single-walled carbon nanotubes, a catalyst of ultrafine particles of about 1 nm is used and manufactured at a high temperature of 900 ° C. There is a problem in that contact with the
[64]
[65]
The average diameter of the carbon nanotubes may be 10 nm to 30 nm, specifically, 10 nm to 15 nm. When the above range is satisfied, the specific surface area of ​​the carbon nanotubes is reduced, so that dispersion in the electrode is easy and a conductive network can be efficiently formed.
[66]
[67]

[68]
[69]
The method for producing carbon nanotubes of the present invention includes preparing an active support by supporting a mixture including a main catalyst precursor and a promoter precursor on a support; preparing a supported catalyst by heat-treating the active support; and introducing a hydrocarbon gas and an inert gas into the fluidized bed reactor in a state where the internal temperature of the fluidized bed reactor in which the supported catalyst is disposed is 500° C. to 700° C. to obtain carbon nanotubes.
[70]
[71]
In the step of preparing the active support, the catalyst may include a main catalyst and a co-catalyst. The main catalyst may be, for example, at least one metal selected from the group consisting of Groups 3 to 12 of the Group 18 Periodic Table of Elements recommended by IUPAC in 1990. Among them, at least one metal selected from the group consisting of 3, 5, 6, 8, 9, and 10 is preferable, and iron (Fe), nickel (Ni), cobalt (Co), chromium (Cr), molybdenum At least one metal selected from (Mo), tungsten (W), vanadium (V), titanium (Ti), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt) and rare earth elements is Especially preferred. In addition, compounds containing a metal element acting as these catalysts, i.e., as catalyst metal precursors, inorganic salts such as nitrates, sulfates and carbonates of catalyst metals, organic salts such as acetates, organic complexes such as acetylacetone complex, organometallic compounds, etc. It will not specifically limit if it is a compound containing a catalyst metal. In particular, the main catalyst may be Co, and the main catalyst precursor is Co(NO 3 ) 2 , Co(NO 3 ) 2 .6H 2 O, Co 2 (CO) 8 , Co 2(CO) 6 [HC=C(C(CH 3 ) 3 )], and Co(CH 3 CO 2 ) 2 It may be preferable to include at least one selected from the group consisting of. When the main catalyst precursor is used, it is possible to synthesize carbon nanotubes at a relatively low temperature compared to other catalysts, and since carbon affinity is low, it is advantageous to shorten the growth unit length of carbon nanotubes. In addition, in the case of the Co catalyst, even if the catalyst is not removed after the carbon nanotube is manufactured, since it does not precipitate on the electrode surface and thus does not form dendrites, it is advantageous in terms of battery stability and battery manufacturing cost.
[72]
In the step of preparing the active support, a cocatalyst may be used in addition to the main catalyst. The reaction activity can be controlled through a cocatalyst. From one or more elements selected from iron (Fe), cobalt (Co) and nickel (Ni) as the co-catalyst, and titanium (Ti), vanadium (V), chromium (Cr), molybdenum (Mo) and tungsten (W) Elements of choice may be used. Among them, preferably, the cocatalyst may include vanadium. Specifically, the promoter precursor may include at least one selected from the group consisting of NH 4 VO 3 , NaVO 3 and V 2 O 5 , V(C 5 H 7 O 2 ) 3 . When the promoter precursor is used, it is easy to manufacture the carbon nanotubes of the present invention having a uniform diameter distribution, a short growth unit structure, and low crystallinity.
[73]
In the step of preparing the active support, in order to prepare an active support in which the main catalyst precursor and the promoter precursor are uniformly supported on a support, the mixture may further include a solvent, and the main catalyst precursor and The promoter precursor may be in a solution state dissolved in a solvent. The solvent may be at least one selected from the group consisting of water, methanol, and ethanol, among which water is preferable.
[74]
The mixture may include the main catalyst precursor and the cocatalyst precursor so that the molar ratio of the main catalyst and the cocatalyst is 10:1 to 1:1, preferably 10:1 to 2.33:1. When the above-described molar ratio is satisfied, the dispersibility of the main catalyst can be remarkably improved while the reactivity of the main catalyst is maintained. In addition, when the catalyst is supported, it is effective to support the main catalyst in a well-dispersed form by controlling the acid point on the surface of the support using a cocatalyst.
[75]
In the step of preparing the active support, the catalyst may be impregnated in the support. The support may include at least one of Al 2 O 3 , SiO 2 , MgO, Mg(NO 3 ) 2 , colloidal silica, and a carbon-based support, wherein the carbon-based support is activated carbon, carbon black , graphite, carbon fiber, graphene, carbon nanotubes, and the like. When the carbon-based support is used, the size and reactivity of the catalyst can be controlled together by controlling the specific surface area and the surface oxygen functional group of the support.
[76]
The catalyst may be included in the support by ultrasonically treating the mixture containing the main catalyst precursor and the promoter precursor together with the retarder, or may be included in the wet impregnation method. In the active support, the catalyst may be included in an amount of 5 to 20 parts by weight, specifically 5 to 10 parts by weight, based on 100 parts by weight of the support.
[77]
The mixture may further include an organic acid that inhibits precipitation of the main catalyst precursor and the promoter precursor, and controls the surface charge of the support by adjusting the pH of the solution. The organic acid may be at least one selected from the group consisting of citric acid, tartaric acid, fumaric acid, malic acid, acetic acid, butyric acid, palmitic acid and oxalic acid, among which citric acid is preferable. The mixture may include the organic acid and the promoter precursor in a weight ratio of 1:0.2 to 1:2, preferably 1:0.5 to 1:1.5. If the above-mentioned range is satisfied, it is possible to suppress the generation of fine powder due to precipitation of the main catalyst and the cocatalyst after the support, and as a result, there is an advantage in that a mixture in a solution state including the main catalyst and the cocatalyst is transparently prepared. If precipitation occurs in the mixture in a solution state, the main catalyst and the co-catalyst may not be uniformly coated on the support, and thus a non-uniform supported catalyst may be prepared. In addition, the non-uniform supported catalyst generates a lot of fine powder during the growth of carbon nanotubes, which may cause trouble in the manufacturing process of carbon nanotubes.
[78]
In the step of heat-treating the active support to prepare a supported catalyst, the heat treatment may be performed at 700° C. to 900° C., specifically, at 700° C. to 850° C. Through the heat treatment, a supported catalyst in which the main catalyst and the promoter are coated on the surface and pores of the support is prepared. In addition, the heat treatment temperature range is one of the reasons that the specific surface area of ​​the finally manufactured carbon nanotubes may be as low as 100 m 2 /g to 196 m 2 /g level. The heat treatment may be performed in an atmospheric atmosphere or an oxygen atmosphere, and may be performed for 5 to 15 hours, specifically 7 to 12 hours. In addition, the heat treatment may be performed in a dry atmosphere (dry air).
[79]
[80]
In the step of obtaining the carbon nanotubes, a fluidized bed reactor may be used. Since the carbon nanotubes of the present invention are manufactured through a fluidized bed reactor, turbulence is likely to occur in the fluidized bed reactor, and the active carrier is mixed with the air flow, so that the growth conditions of the carbon nanotubes may not be constant. Accordingly, carbon nanotubes having a short growth unit length, low crystallinity, and close to a bamboo shape may be manufactured. If a fixed-bed reactor is used, strict control of reaction conditions such as reaction temperature, concentration, flow rate, and time must be accompanied to produce carbon nanotubes close to the carbon nanotubes of the present invention, as well as to increase the yield not high Therefore, it is preferable to use a fluidized bed reactor to simplify the process and reduce manufacturing cost.
[81]
In particular, the fluidized bed reactor is a fluidized bed reactor having a capacity of the internal reaction vessel of 0.5 m 3 or more, specifically 1.0 m 3 or more, more specifically 1.0 m 3 to 6.0 m 3 , for example, 1.0 m 3 to 3.0 m 3 . it is preferable This means that it has a very large capacity compared to a conventional fluidized bed reactor, whereby a high flow rate turbulence can be easily formed in the fluidized bed reactor, and there is an advantage in that the internal temperature changes greatly. Accordingly, the carbon nanotube of the present invention can be smoothly manufactured.
[82]
In order to obtain the carbon nanotubes, hydrocarbon gas and inert gas may be introduced into the fluidized bed reactor in which the supported catalyst is disposed. That is, in the above step, the chemical vapor synthesis method may be performed.
[83]
In more detail, first, the supported catalyst may be introduced into the fluidized bed reactor. Subsequently, the hydrocarbon gas, or the hydrocarbon gas and inert gas are injected at a temperature above the pyrolysis temperature of the gaseous hydrocarbon gas or below the melting point of the catalyst supported on the supported catalyst, and the gaseous hydrocarbon gas Through decomposition, carbon nanotubes can be grown by chemical vapor synthesis. At this time, the hydrocarbon gas and the inert gas may be injected in the form of a mixed gas, and the injected gas may further include a reducing gas.
[84]
The hydrocarbon gas may be a carbon-based compound having 6 or less carbon atoms, and any material that can exist in a gaseous phase at a temperature of 150° C. or higher may be used without particular limitation. Specifically, the hydrocarbon gas is at least selected from the group consisting of carbon monoxide, methane, ethane, ethylene, ethanol, acetylene, propane, propylene, butane, butadiene, pentane, pentene, cyclopentadiene, hexane, cyclohexane, benzene and toluene. may include any one. However, the present invention is not necessarily limited thereto.
[85]
The inert gas may include at least one selected from the group consisting of nitrogen and hydrogen, and may preferably include nitrogen and hydrogen. The inert gas carries hydrocarbon gas, suppresses combustion of carbon nanotubes, and helps decomposition of hydrocarbon gas.
[86]
The hydrocarbon gas and the inert gas may be used in a volume ratio of 0.1 to 10: 1 to 11, specifically 0.5 to 1.5: 1.5 to 3.0 by volume. Of these, the inert gas contains only nitrogen, or nitrogen and hydrogen in a volume ratio of 1: 0.01 to 10, specifically 1; It may be included in a volume ratio of 0.5 to 1.5.
[87]
The inflow rate of the mixed gas including the hydrocarbon gas and the inert gas may be 10 sccm to 50,000 sccm, specifically 1,000 sccm to 45,000 sccm, and more specifically 6,000 sccm to 30,000 sccm.
[88]
[89]
Step of introducing hydrocarbon gas and an inert gas into the fluidized bed reactor in a state in which the internal temperature of the fluidized bed reactor in which the supported catalyst is disposed is 500° C. to 700° C. to obtain carbon nanotubes
[90]
In the step of obtaining the carbon nanotubes, the internal temperature of the fluidized bed reactor may be 500 °C to 720 °C, specifically 600 °C to 720 °C, and more specifically 620 °C to 720 °C. When the temperature is less than 500° C., the amount of unreacted hydrocarbon gas is excessively increased and there is a problem in that the yield is reduced. When the temperature is higher than 720° C., there is a problem of a reduction in yield due to thermal decomposition of hydrocarbon gas.
[91]
The step of obtaining the carbon nanotubes may be performed for 0.5 to 10 hours, specifically for 0.5 to 5 hours, and more specifically for 0.7 to 3 hours. In other words, the range means the time for reacting the hydrocarbon gas in the fluidized bed reactor in the presence of the supported catalyst. When the above range is satisfied, the synthesis yield of carbon nanotubes controlled to have a short growth unit length can be maximized.
[92]
In the step of obtaining the carbon nanotubes, a reducing gas such as hydrogen may be additionally introduced.
[93]
That is, in order to produce the carbon nanotubes of the present invention, the main catalyst, co-catalyst, hydrocarbon gas inflow rate, inert gas inflow rate, fluidized bed reactor, and time for reacting the hydrocarbon gas in the fluidized bed reactor are All must be adjusted to an appropriate level.
[94]
[95]

[96]
[97]
An electrode according to another embodiment of the present invention may include the carbon nanotubes of the above-described embodiment. Since the carbon nanotube included in the electrode is the same as the carbon nanotube of the above-described embodiment, a description of the carbon nanotube will be omitted below.
[98]
[99]
The electrode may be at least one of an anode and a cathode.
[100]
The electrode may include an electrode active material layer, and in some cases, the electrode may include a current collector and an electrode active material layer disposed on the current collector.
[101]
The current collector may have conductivity without causing chemical change in the battery, and is not particularly limited. For example, as the current collector, copper, stainless steel, aluminum, nickel, titanium, fired carbon, or a surface of aluminum or stainless steel treated with carbon, nickel, titanium, silver, or the like may be used. Specifically, a transition metal that easily adsorbs carbon, such as copper or nickel, may be used as the current collector.
[102]
The electrode active material layer may include active material particles.
[103]
When the electrode is a positive electrode, the active material particles may include positive active material particles that are commonly used. Specifically, the positive active material may include a layered compound such as lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), or a compound substituted with one or more transition metals; lithium iron oxides such as LiFe 3 O 4 ; Lithium manganese oxides such as Formula Li 1+c1 Mn 2-c1 O 4 (0≤c1≤0.33), LiMnO 3 , LiMn 2 O 3 , and LiMnO 2 ; lithium copper oxide (Li 2 CuO 2 ); LiV 3 O 8 , V 2 O 5 , Cu vanadium oxides such as 2 V 2 O 7 ; Formula LiNi 1-c2 M c2 O 2 (where M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and satisfies 0.01≤c2≤0.3) Ni site-type lithium nickel oxide; Formula LiMn 2-c3 M c3 O 2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and satisfies 0.01≤c3≤0.1) or Li 2 Mn 3 MO 8 (herein, M is at least one selected from the group consisting of Fe, Co, Ni, Cu and Zn.) lithium manganese composite oxide; LiMn 2 O 4 in which part of Li in the formula is substituted with alkaline earth metal ions, and the like, but are not limited thereto.
[104]
When the electrode is an anode, the active material particles may include positive active material particles that are commonly used. Specifically, the negative active material particles may include graphite-based active material particles or silicon-based active material particles. The graphite-based active material particles may use at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fiber and graphitized mesocarbon microbeads, and in particular, when artificial graphite is used, rate characteristics can be improved. . The silicon-based active material particles are Si, SiO x (0
[108]
[109]
A secondary battery according to another embodiment of the present invention may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is the electrode of the other embodiment described above can be
[110]
The separator separates the anode and the anode and provides a passage for lithium ions to move, and can be used without any particular limitation as long as it is normally used as a separator in a secondary battery. Excellent is preferred. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these A laminated structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.
[111]
The electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, and a molten inorganic electrolyte, which can be used in manufacturing a lithium secondary battery.
[112]
Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.
[113]
As the non-aqueous organic solvent, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butylolactone, 1,2-dime ethoxyethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, Methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, pyropion An aprotic organic solvent such as methyl acid or ethyl propionate may be used.
[114]
In particular, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are highly viscous organic solvents and have a high dielectric constant and thus well dissociate lithium salts. If the same low-viscosity, low-dielectric constant linear carbonate is mixed in an appropriate ratio, an electrolyte having high electrical conductivity can be prepared, which can be more preferably used.
[115]
A lithium salt may be used as the metal salt, and the lithium salt is a material readily soluble in the non-aqueous electrolyte. For example, as an anion of the lithium salt , F - , Cl - , I - , NO 3 - , N(CN) ) 2 - , BF 4 - , ClO 4 - , PF 6 - , (CF 3 ) 2 PF 4 - , (CF 3 ) 3 PF 3 - , (CF 3 ) 4 PF 2 - , (CF 3 )) 5 PF - , (CF 3 ) 6 P - , CF 3 SO 3 - , CF 3 CF 2 SO 3 - , (CF 3 SO 2 ) 2 N - , (FSO 2 ) 2 N - , CF 3 CF 2 ( CF 3 ) 2 CO - , (CF 3 )SO 2 ) 2 CH - , (SF 5 ) 3 C - , (CF 3 SO 2 ) 3 C - , CF 3 (CF 2 ) 7 SO 3 - , CF 3 CO 2 - , CH 3 CO 2 - , SCN - and (CF 3 CF 2 SO 2 ) 2One selected from the group consisting of N − may be used.
[116]
In addition to the electrolyte components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, tri Ethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives such as jolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol or aluminum trichloride may be further included.
[117]
[118]
According to another embodiment of the present invention, there is provided a battery module including the secondary battery as a unit cell and a battery pack including the same. Since the battery module and the battery pack include the secondary battery having high capacity, high rate-rate characteristics and cycle characteristics, a medium-to-large device selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems can be used as a power source for
[119]
[120]
Hereinafter, preferred embodiments are presented to help the understanding of the present invention, but the embodiments are merely illustrative of the present disclosure, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present disclosure, It goes without saying that such variations and modifications fall within the scope of the appended claims.
[121]
[122]
Examples and Comparative Examples
[123]
[124]
Example 1: Preparation of carbon nanotubes
[125]
(1) Preparation of supported catalyst
[126]
An aluminum oxide support obtained by calcining aluminum hydroxide (Aluminum-tri-hydroxide, Al(OH) 3 ) at 250 to 500° C. is used.
[127]
Co-V metal catalyst is prepared by adding Co(NO 3 ) 2 6H 2 O as a precursor material of Co and NH 4 VO 3 , citric acid as a precursor material of V together, and the molar ratio of Co:V is 10:1. do. Finally, the above-described Co-V catalyst and the support were stirred in water in a constant temperature bath at 60° C. at a ratio of 1: 10, and then the vacuum-dried supported catalyst was calcined at 700° C. or higher in dry air for 10 hours. Thus, a supported catalyst was prepared.
[128]
(2) Manufacture of carbon nanotubes
[129]
After disposing the above-described supported catalyst in a fluidized bed reactor (Pilot Scale Reactor (capacity of internal reaction vessel: 1 m 3 )), in the fluidized bed reactor having an internal temperature of 700° C., ethylene: hydrogen: nitrogen is 1: 1: 5 The mixed gas mixed in the volume ratio was introduced at an inflow rate of 7,000 sccm to prepare carbon nanotubes having an average diameter of 12 nm.
[130]
[131]
Example 2: Preparation of carbon nanotubes
[132]
Carbon having an average diameter of 12 nm in the same manner as in Example 1, except that a Commercial Scale Reactor (capacity of the internal reaction vessel: 4 m 3 ) was used as the fluidized bed reactor, and the inflow rate of the mixed gas was changed to 28,000 sccm. Nanotubes were prepared.
[133]
[134]
Comparative Example 1: Preparation of carbon nanotubes
[135]
Among commercial products of C-Nano , carbon nanotubes having an average diameter of 10 nm and a specific surface area of ​​238 m 2 /g were prepared.
[136]
[137]
Comparative Example 2: Preparation of carbon nanotubes
[138]
Among commercial products of BTR , carbon nanotubes having an average diameter of 10 nm and a specific surface area of ​​249 m 2 /g were prepared.
[139]
[140]
Comparative Example 3: Preparation of carbon nanotubes
[141]
Among commercial products of BTR , carbon nanotubes having an average diameter of 45 nm and a specific surface area of ​​85 m 2 /g were prepared.
[142]
[143]
Comparative Example 4: Preparation of carbon nanotubes
[144]
Among commercial products of JEIO , carbon nanotubes having an average diameter of 8 nm and a specific surface area of ​​350 m 2 /g were prepared.
[145]
[146]
The physical properties of the carbon nanotubes of Examples 1 and 2 and Comparative Examples 1 to 4 are summarized in Tables 1 and 2.
[147]
[148]
[Table 1]
A: La(001)(nm) before graphitization B: La (001) (nm) after graphitization BA (nm) C: Lc (002) (nm) before graphitization D: Lc (002) (nm) after graphitization DC (nm) specific surface area (m 2 /g)
Example 1 6.8 7.6 0.8 4.0 4.0 0.0 181
Example 2 6.7 7.5 0.8 3.9 4.0 0.1 185
Comparative Example 1 7.2 7.8 0.6 3.3 3.5 0.2 238
Comparative Example 2 7.1 7.7 0.6 3.8 4.0 0.2 249
Comparative Example 3 6.8 7.8 1.0 15.4 15.7 0.3 85
Comparative Example 4 6.9 6.1 1.2 2.5 2.5 0.0 350
[149]
The La(100) and Lc(002) were derived by measuring carbon nanotubes by X-ray diffraction analysis (XRD). Specifically, XRD analysis was performed using Bruker AXS D4 Endeavor XRD (voltage: 40 kV, current: 40 mA), Cu Ka radiation (wavelength: 1.54 Å, 2-Theta 10° to 90° every 0.02° 87.5 Among the measurement results, 2θ is the full width at half maximum (FWHM, Full Width at Half-Maximum) of the (002) crystal peak that appears near 20° to 30° and (100) appears near 38° to 50°. ) was measured and the full width at half maximum of the crystal peak was calculated using Scherrer's formula to obtain Lc (002) and La (100) values.
[150]
The specific surface area was measured by the BET method, and specifically, the amount of nitrogen gas adsorbed under liquid nitrogen temperature (77 K) was calculated using BELSORP-mini II manufactured by BEL Japan.
[151]
[152]
[Table 2]
E: A D /A G before graphitization F: A D /A G after graphitization EF G: Half width before graphitization (cm -1 ) H: Half width after graphitization (cm -1 ) GH (cm -1 ) Oxygen atom-containing functional group content (% by weight)
Example 1 0.94 0.40 0.54 63.5 38.8 24.7 1.8
Example 2 0.98 0.39 0.59 63.6 39.3 24.3 1.9
Comparative Example 1 0.73 0.36 0.37 48.0 39.2 8.8 0.2
Comparative Example 2 0.87 0.41 0.46 54.6 39.8 14.8 1.0
Comparative Example 3 0.99 0.41 0.58 65.2 39.6 25.6 1.7
Comparative Example 4 1.24 0.36 0.88 72.3 41.1 31.2 2.6
[153]
The A D /A G ratio is a Raman spectrum measured after obtaining a spectrum through Raman Mapping (using ×4 Object) at 100 points using Raman spectrum analysis equipment (NRS-2000B, Jasco), 532 nm laser corresponds to the D/G peak ratio after averaging. Here, the full width at half maximum of the G peak corresponds to the width of the horizontal axis corresponding to the half of the maximum vertical axis value of the highest peak. It was measured It was measured.
[154]
[155]
Experimental Example 1: Confirmation of the structure of carbon nanotubes
[156]
Each of the carbon nanotubes of Example 1 and Comparative Example 1 was observed through TEM and shown in FIG. 1 . Specifically, FIG. 2 is a TEM photograph of the carbon nanotube of Example 1 before graphitization at 2500° C. (FIG. 2(a), (b)) and the graphitized carbon nanotube of Example 1 It is a TEM photograph (FIG. 2(c), (d)). 3 is a TEM photograph of the carbon nanotube of Comparative Example 1 before graphitization at 2500° C. (FIG. 3 (a), (b)) and a TEM photograph of the carbon nanotube of Comparative Example 1 subjected to the graphitization treatment ( 3 (c), (d)).
[157]
Comparing FIGS. 2 (a) and (b) with FIGS. 3 (a) and (b), the carbon nanotube of Example 1 has more nodes (curved portions) than the carbon nanotube of Comparative Example 1. You can see that it has a lot, and it has a less straight shape.
[158]
In addition, if you look at (a), (b) and 3 (a), (b) of FIG. 2 as well as (c), (d) and 3 (c), (d) of FIG. 2 together, It can be more easily confirmed that the carbon nanotube of Example 1 has a relatively short growth unit structure. Specifically, after the graphitization treatment, Example 1 has a straight shape for each growth unit (the length between nodes and nodes), and it can be seen that one linear unit and a linear unit adjacent thereto are bent at a predetermined angle. have. On the other hand, in the case of Comparative Example 2, the bent structure observed in FIG. 2 was not seen even after the graphitization treatment.
[159]
[160]
Experimental Example 2: Powder resistance of carbon nanotubes
[161]
For the carbon nanotubes of Examples 1 and 2 and Comparative Examples 1 to 4, the carbon nanotube powder resistance was measured as follows.
[162]
Using Loresta-GX (MCP-PD51) equipment, fill the sample holder with 0.5 g of carbon nanotube powder, press at 400, 800, 1200, 1600, 2000 kN, and the powder resistance value at 60 MPa (Ohm cm) was evaluated.
[163]
[164]
Experimental Example 3: Powder resistance of electrode slurry
[165]
Using the carbon nanotubes of Examples 1 and 2 and Comparative Examples 1 to 4, electrode slurries were prepared in the following manner.
[166]
A cathode active material Li[Ni 0.6 Mn 0.2 Co 0.2 ]O 2 , each of the above-described carbon nanotube conductive materials, polyvinylidene fluoride (PVdF) as a binder, H-NBR as a dispersant, and NMP as a solvent were mixed / stirred. Then, a positive electrode slurry having a solid content of 72% was prepared. The weight ratio of the positive electrode active material, the carbon nanotubes, PVdF, and H-NBR in the positive electrode slurry was 96.2:1.5:2.0:0.3.
[167]
Thereafter, the powder resistance of the electrode slurry was measured by the following method.
[168]
The electrode slurries prepared using the carbon nanotubes of Examples 1 and 2 to Comparative Examples 1 to 4 were vacuum dried at a temperature of 130° C. for 3 hours, and then pulverized to prepare a powder. Thereafter, using Loresta GP equipment from Mitsubishi Chem Analytic, pellets were prepared at 25° C. and 9.8 MPa load in an atmosphere of 50% relative humidity. Thereafter, the powder resistance was measured by the 4-probe method.
[169]
[170]
Experimental Example 4: Evaluation of battery capacity retention (lifetime characteristics)
[171]
Using each electrode slurry prepared in Experimental Example 3, an electrode was prepared in the following manner.
[172]
The electrode slurry was applied to a positive electrode current collector (Al) having a thickness of 20 μm so that the solid content (loading amount) was 21 mg/cm 2 , and dried. Thereafter, the current collector on which the positive electrode slurry was disposed was rolled by a roll rolling method to adjust the total thickness to 77 μm. Thereafter, the current collector was dried in a vacuum oven at 130° C. for 6 hours to prepare a positive electrode.
[173]
An anode slurry was prepared by mixing artificial graphite as an anode active material, carbon black as an anode conductive material, styrene butadiene rubber (SBR) as an anode binder, and carboxymethyl cellulose (CMC) in distilled water in a weight ratio of 96.1:0.5:2.3:1.1, respectively. The prepared slurry was applied and dried to a weight (loading amount) of 10 mg/cm 2 on a negative electrode current collector (Cu) having a thickness of 20 μm. Thereafter, the current collector on which the negative electrode slurry was formed was rolled by a roll rolling method, and the final thickness (current collector + active material layer) was adjusted to 80 μm. Thereafter, the current collector was dried in a vacuum oven at 110° C. for 6 hours to prepare a negative electrode.
[174]
Thereafter, a monocell was prepared by combining the prepared negative electrode and positive electrode with a polyethylene separator having a thickness of 15 μm interposed therebetween, and then, an electrolyte solution (ethylene carbonate (EC)/ethylmethyl carbonate (EMC)) in the monocell. = 1/2 (volume ratio), lithium hexafluorophosphate (LiPF6 1 mol)) was injected to prepare a lithium secondary battery.
[175]
Thereafter, the capacity retention rate of the battery was evaluated by the following method.
[176]
The lithium secondary batteries prepared in Examples 1 and 2 and Comparative Examples 1 to 4 were fixed at 45° C., the charging C-Rate was 1.0 C, and the discharging C-Rate was 1.0 C, and high-temperature life evaluation was performed, 100 The capacity retention rate (%) in the cycle was evaluated.
[177]
[178]
Table 3 shows the results of Experimental Examples 2 to 4.
[179]
[180]
[Table 3]
Powder resistance of carbon nanotubes (Ω cm) Powder resistance of electrode slurry (Ω cm) Battery capacity retention rate (%)
Example 1 0.012 66 97.8
Example 2 0.013 69 97.6
Comparative Example 1 0.012 75 96.2
Comparative Example 2 0.013 72 96.5
Comparative Example 3 0.014 83 95.1
Comparative Example 4 0.017 77 95.8

WE CLAIMS

XRD measurements, a La (100) is less than 7.0nm, a specific surface area of 100m 2 / g to 196m 2 carbon nanotubes / g.
[Claim 2]
The carbon nanotube of claim 1, wherein BA is 0.70 nm or more: A is La(100) (unit: nm) when XRD measurement of the carbon nanotube before graphitization at 2500° C., and B is the In XRD measurement of the graphitized carbon nanotubes, La(100) (unit: nm).
[Claim 3]
The carbon nanotube according to claim 1, wherein the carbon nanotube includes a functional group containing an oxygen atom, and the functional group containing the oxygen atom is 1.2 wt% or more in the carbon nanotube.
[Claim 4]
The carbon nanotube according to claim 1, wherein DC is 0.18 nm or less: wherein C is Lc (002) (unit: nm) when XRD measurement of the carbon nanotube before graphitization at 2500° C., and D is the In XRD measurement of the graphitized carbon nanotube, Lc(002) (unit: nm).
[Claim 5]
The carbon nanotube according to claim 1, wherein, when measuring a Raman spectrum, A D /A G is 0.90 or more.
[Claim 6]
The method according to claim 1, Carbon nanotube having an EF of 0.50 or more: When E is a Raman spectrum measurement for the carbon nanotube before graphitization at 2500° C., A D /A G , and F is the graphitized process. When measuring a Raman spectrum for the carbon nanotube, A D /A G is.
[Claim 7]
The carbon nanotube according to claim 1, which is a multi-walled carbon nanotube.
[Claim 8]
The carbon nanotube according to claim 1, wherein the carbon nanotube has an average diameter of 10 nm to 30 nm.
[Claim 9]
An electrode comprising the carbon nanotube of claim 1.
[Claim 10]
A secondary battery comprising the electrode of claim 9 .