Positive electrode for lithium secondary battery, method for manufacturing same, and lithium secondary battery comprising same

Abstract

A positive electrode for a lithium secondary battery and a lithium secondary battery including the same are provided. The positive electrode includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material and a conductive material, and a Raman R1 value represented by A1D / A1G measured on a surface of the positive electrode active material layer is in a range of 1.5 to 4.

Description

[0001] Cross - reference to related applications and claim of priority

[0002] This application claims priority to a Korean Patent Application No. 10 - 2023 - 0188664, filed on December 21, 2023, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] Embodiments of the present disclosure generally relate to a positive electrode for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. More particularly, embodiments relate to a positive electrode for a lithium secondary battery including a carbon - based material, a method for manufacturing the same, and a lithium secondary battery including the same. Background Art

[0004] With the development of information and display technologies, rechargeable secondary batteries have been widely used as power sources for mobile electronic devices (such as cameras, mobile phones, laptop computers, etc.). Recently, battery packs including secondary batteries are being developed and applied as eco - friendly power sources for electric vehicles, hybrid vehicles, etc.

[0005] Examples of secondary batteries include lithium secondary batteries, nickel - cadmium batteries, nickel - metal hydride batteries, etc. Among secondary batteries, lithium secondary batteries are actively developed due to their high operating voltage, high energy density per unit weight, high charging speed, and small size.

[0006] Generally, a lithium secondary battery may include an electrode assembly, an electrolyte impregnating the electrode assembly, and a case encapsulating the electrode assembly, and the electrode assembly includes a positive electrode and a negative electrode stacked repeatedly. For example, the case of a lithium secondary battery may be pouch - shaped for accommodating the electrode assembly and the electrolyte.

[0007] Recently, since lithium secondary batteries are applied to large - capacity batteries such as electric vehicle batteries, electrode components or electrode structures capable of providing higher capacity and high power are being studied and developed.

[0008] For example, it has been proposed to apply a carbon - based conductive material to the positive electrode to improve the conductivity of the positive electrode. However, in the process of manufacturing the positive electrode / cell, due to the distribution characteristics and crystal characteristics of the conductive material or the positive electrode active material, uniform electrochemical characteristics of the entire positive electrode / cell may not be provided. Summary of the Invention

[0009] According to an embodiment of the present disclosure, there is provided a positive electrode for a lithium secondary battery having improved capacity characteristics and stability.

[0010] According to an embodiment of the present disclosure, there is provided a method for preparing a positive electrode for a lithium secondary battery having improved capacity characteristics and stability.

[0011] According to another embodiment of the present disclosure, a lithium secondary battery having improved capacity characteristics and stability is provided.

[0012] A positive electrode for a lithium secondary battery includes a positive electrode current collector and a positive electrode active material layer formed on a surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and a conductive material. A Raman R1 value represented by Equation 1, measured on the surface of the positive electrode active material layer, is in a range of 1.5 to 4.0.

[0013] Equation 1

[0014] Raman R1 = A1 D / A1 G

[0015] In Equation 1, A1 D is the peak area of the absorption region from 1252 cm -1 to 1445 cm -1 in the Raman spectrum measured using a Renishaw InVia Raman microscope at a 100% laser focus level, and A1 G is the peak area of the absorption region from 1577 cm -1 to 1620 cm -1 in the Raman spectrum measured using a Renishaw InVia Raman microscope at a 100% laser focus level.

[0016] In some embodiments, the Raman R1 value may be in a range of 1.6 to 3.8.

[0017] In some embodiments, the conductive material may include at least one of carbon black and carbon nanotubes.

[0018] In some embodiments, the conductive material may include carbon black having a Raman R2 value defined by Equation 2 in a range of 2.5 to 3.5.

[0019] Equation 2

[0020] Raman R2 = A2 D / A2 G

[0021] In Equation 2, A2 D is the peak area of the absorption region from 1252 cm -1 to 1445 cm -1 in the Raman spectrum measured using a Renishaw InVia Raman microscope at a 0% laser focus level, and A2 GThe peak area of the absorption region from 1577 cm -1 to 1620 cm -1 in the Raman spectrum measured using an InVia Raman microscope from Renishaw at a laser focusing level of 0%.

[0022] In some embodiments, the conductive material may include carbon nanotubes with a Raman R2 value defined by Equation 2 in the range of 1.8 to 2.8.

[0023] Equation 2

[0024] Raman R2 = A2 D / A2 G

[0025] In Equation 2, A2 D is the peak area of the absorption region from 1252 cm -1 to 1445 cm -1 in the Raman spectrum measured using an InVia Raman microscope from Renishaw at a laser focusing level of 0%, and A2 G is the peak area of the absorption region from 1577 cm -1 to 1620 cm -1 in the Raman spectrum measured using an InVia Raman microscope from Renishaw at a laser focusing level of 0%.

[0026] In some embodiments, the conductive material may include carbon black and carbon nanotubes.

[0027] In some embodiments, the mixing weight ratio of the carbon black to the carbon nanotubes may be from 3:7 to 7:3.

[0028] In some embodiments, the positive electrode active material may include lithium nickel metal oxide, the lithium nickel metal oxide further includes cobalt element, and the molar ratio of cobalt in the lithium nickel metal oxide among elements other than lithium and oxygen may be 0.1 or less.

[0029] In some embodiments, the positive electrode active material may include lithium nickel metal oxide, and the molar ratio of nickel in the lithium nickel metal oxide among elements other than lithium and oxygen may be 0.8 or greater.

[0030] In some embodiments, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material may be in the range of 90 wt% to 98 wt%, and the content of the conductive material may be in the range of 0.5 wt% to 5 wt%.

[0031] A lithium secondary battery includes the positive electrode for the lithium secondary battery described above and a negative electrode opposite to the positive electrode.

[0032] In a method of manufacturing a positive electrode for a lithium secondary battery, a primary solution mixed with a positive electrode binder and a conductive material is prepared; a positive electrode slurry is prepared by mixing a positive electrode active material into the primary solution; and the positive electrode slurry is coated on a positive electrode current collector.

[0033] In some embodiments, in the preparation of the primary solution, a positive electrode binder solution and a conductive material solution may be separately prepared. The positive electrode binder solution and the conductive material solution may be mixed.

[0034] In some embodiments, the solid content of the conductive material solution may be in the range of 4 wt% to 15 wt%.

[0035] In some embodiments, the solid content of the binder solution may be in the range of 5 wt% to 20 wt%.

[0036] In some embodiments, the solid content of the positive electrode slurry may be in the range of 60 wt% to 80 wt%.

[0037] In some embodiments, the coated positive electrode slurry may be dried and pressed to form a positive electrode active material layer. The Raman R1 value represented by Equation 1 measured on the surface of the positive electrode active material layer may be in the range of 1.5 to 4.0.

[0038] According to an embodiment of the present disclosure, a positive electrode for a lithium secondary battery includes a carbon-based conductive material and may have improved conductivity and power characteristics. The positive electrode active material layer included in the positive electrode may have a Raman area ratio range measured under specific focusing level conditions. Within the above range, improved conductivity may be uniformly provided over the entire positive electrode active material layer, and stable high power characteristics may be achieved.

[0039] The positive electrode and the lithium secondary battery according to the present disclosure can be widely applied to the field of green technologies, such as electric vehicles, battery charging stations, solar power generation using batteries, wind power generation, etc. The positive electrode and the lithium secondary battery according to the present disclosure can be used in eco-friendly electric vehicles and hybrid vehicles, etc., to prevent climate change by suppressing air pollution and greenhouse gas emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic cross-sectional view showing a positive electrode for a lithium secondary battery according to an embodiment of the present disclosure.

[0041] Figure 2 and Figure 3 are schematic views for describing the measurement of the Raman area ratio at a laser focusing level of 0% and a laser focusing level of 100%, respectively.

[0042] Figure 4 and Figure 5It is a flowchart for describing a method of manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present disclosure.

[0043] Figure 6 and Figure 7 are respectively a schematic plan view and a schematic cross-sectional view of a lithium secondary battery according to an embodiment of the present disclosure. Detailed Description of the Invention

[0044] According to an embodiment disclosed in the present application, there is provided a positive electrode for a lithium secondary battery having a Raman area ratio within a predetermined range. According to an embodiment of the present disclosure, there is also provided a lithium secondary battery including the positive electrode.

[0045] Hereinafter, the technical scope of the present disclosure will be described in detail with reference to the accompanying drawings and embodiments. However, these embodiments are provided only as examples, and the present disclosure is not limited to the specific embodiments disclosed herein.

[0046] Figure 1 is a schematic cross-sectional view of a positive electrode for a lithium secondary battery according to an embodiment of the present disclosure.

[0047] Referring to Figure 1 , the positive electrode 100 for a lithium secondary battery (hereinafter simply referred to as the positive electrode) may include a positive electrode current collector 105 and a positive electrode active material layer 110.

[0048] For example, the positive electrode current collector 105 may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector may include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. For example, the thickness of the positive electrode current collector 105 may be in the range of 5 μm to 50 μm.

[0049] For example, the positive electrode paste may be prepared by mixing the positive electrode active material in a solvent. The positive electrode paste may be coated on the positive electrode current collector 105 and then dried and pressed to prepare the positive electrode active material layer 110. The coating process may include any suitable method, such as including gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc. The positive electrode paste may further include a binder and a conductive material.

[0050] Non-limiting examples of solvents for preparing the positive electrode paste may include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0051] In some embodiments, the positive electrode paste may be prepared by pre-dispersing the conductive material and the binder, and then mixing and stirring the positive electrode active material. The method for preparing the positive electrode paste will be described in more detail with reference to Figure 4 and Figure 5 More specifically, the method for preparing the positive electrode paste will be described.

[0052] The positive electrode active material may include a compound into which lithium ions can be reversibly inserted and extracted.

[0053] In some embodiments, the positive electrode active material may include a lithium nickel metal oxide. The lithium nickel metal oxide may further include at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0054] In some embodiments, the positive electrode active material or the lithium nickel metal oxide may include a layered structure or a crystal structure represented by Chemical Formula 1.

[0055] Chemical formula 1

[0056] Li x Ni a M b O 2+z

[0057] In Chemical Formula 1, 0.9 ≤ x ≤ 1.5, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b ≤ 0.4, and -0.5 ≤ z ≤ 0.1. As described above, M may include Co, Mn, and / or Al.

[0058] The chemical structure represented by Chemical Formula 1 represents the bonding relationship included in the layered structure or the crystal structure of the positive electrode active material, and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn may be used as the main active elements of the positive electrode active material together with Ni. Chemical Formula 1 is provided to represent the bonding relationship of the main active elements, and it should be understood that Chemical Formula 1 encompasses the chemical formulas with additional elements introduced and substituted by additional elements.

[0059] In one embodiment, in addition to the main active elements, auxiliary elements for enhancing the chemical stability of the positive electrode active material or the layered structure / crystal structure may be included. The auxiliary elements may be bonded to the layered structure / crystal structure to form bonds, and it should be understood that this situation is included within the scope of the chemical structure represented by Chemical Formula 1.

[0060] The auxiliary elements may include, for example, at least one of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr. The auxiliary elements may be used as auxiliary active elements, such as Al, which, together with Co or Mn, contributes to the capacity / power activity of the positive electrode active material.

[0061] For example, the positive electrode active material or the lithium nickel metal oxide particles may include a layered structure or a crystal structure represented by Chemical Formula 1-1.

[0062] Chemical formula 1-1

[0063] Li x Ni a M1 b1 M2 b2 O 2+z

[0064] In Chemical Formula 1-1, M1 may include Co, Mn, and / or Al. M2 may include the above-mentioned auxiliary elements. In Chemical Formula 1-1, 0.9 ≤ x ≤ 1.2, 0.6 ≤ a ≤ 0.99, 0.01 ≤ b1 + b2 ≤ 0.5, and -0.5 ≤ z ≤ 0.1.

[0065] The above positive electrode active material may further include a coating element or a doping element. For example, elements that are substantially the same as or similar to the above-mentioned auxiliary elements may be used as the coating element or the doping element. For example, the above elements may be used alone or in combination of two or more of them to be used as the coating element or the doping element.

[0066] The coating element or the doping element may be present on the surface of the lithium nickel metal oxide particles, or may penetrate through the surface of the lithium nickel metal oxide particles to be included in the bonding structure represented by Chemical Formula 1 or Chemical Formula 1-1.

[0067] The positive electrode active material may include nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, NCM-based lithium oxide with an increased nickel content may be used.

[0068] Ni may be provided as a transition metal related to the power and capacity of the lithium secondary battery. Therefore, a high-capacity positive electrode and a high-capacity lithium secondary battery may be achieved by using a high Ni component in the positive electrode active material as described above.

[0069] However, as the Ni content increases, the long-term storage stability and life stability of the positive electrode or the secondary battery may be relatively reduced, and the side reactions with the electrolyte may also increase. However, according to various embodiments, Mn may be used to improve the life stability and capacity retention characteristics, while Co is used to maintain the conductivity.

[0070] The Ni content in the NCM-based lithium oxide (e.g., the mole fraction of Ni based on the total moles of Ni, Co, and Mn) can be 0.6 or greater, 0.7 or greater, or 0.8 or greater. In some embodiments, the Ni content can be in the range of 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0071] In some embodiments, the positive electrode active material can include a low-Co active material or a Co-free active material having a reduced Co content. For example, based on the total moles of Ni, Co, and Mn among the elements other than Li and O in the positive electrode active material, the molar ratio of Co can be 0.2 or less, 0.1 or less, 0.09 or less, 0.08 or less, 0.06 or less, or 0.05 or less.

[0072] Even when the Co content is reduced, improved conductivity can be achieved by adjusting the Raman R1 value (which will be described below), and a high-Ni component can be effectively introduced.

[0073] In some embodiments, the positive electrode active material can include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (such as LiFePO4).

[0074] In some embodiments, the positive electrode active material can include a Mn-rich active material, a Li-rich layered oxide (LLO) / Over-Lithiated Oxide (OLO)-based active material, a Co-free active material, etc., which can have a chemical structure or crystal structure represented by Chemical Formula 2 below.

[0075] Chemical Formula 2

[0076] p[Li2MnO3]·(1-p)[Li q JO2]

[0077] In Chemical Formula 2, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J can include at least one element selected from Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0078] The binder may include polyvinylidene fluoride (PVDF), poly(vinylidenefluoride-co-hexafluoropropylene), polyacrylonitrile, polymethyl methacrylate, acrylonitrile-butadiene rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), polyacrylic acid-based binder, poly(3,4-ethylenedioxythiophene) (PEDOT)-based binder, etc. In some embodiments, a PVDF-based binder may be used as the positive electrode binder.

[0079] A conductive material may be added to enhance conductivity and / or the mobility of lithium ions or electrons. Non-limiting examples of the conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber; and / or metal-based conductive materials such as tin, tin oxide, titanium oxide, and perovskite materials such as LaSrCoO3, LaSrMnO3, etc.

[0080] In some embodiments, a carbon-based conductive material may be used as the conductive material. In some embodiments, carbon black and / or carbon nanotube (CNT) may be used as the conductive material. For example, multi-walled carbon nanotube (MWCNT) may be used as the carbon nanotube.

[0081] In one embodiment, a mixture of carbon black and carbon nanotubes may be used as the conductive material. In this case, the mixing weight ratio of carbon black and carbon nanotubes may be in the range of 2:8 to 8:2, 3:7 to 7:3, or 4:6 to 6:4. Within the above range, the amorphous characteristics of carbon black and the high conductive characteristics of carbon nanotubes can be balanced.

[0082] In one embodiment, graphite may be used as the conductive material.

[0083] According to an embodiment of the present disclosure, the Raman R1 value defined by Equation 1 measured on the surface of the positive electrode active material layer 110 may be in the range of 1.5 to 4.0. For example, the Raman R1 value may be measured on the surface of the positive electrode active material layer 110, which is the opposite surface of the surface in contact with the positive electrode current collector 105.

[0084] Equation 1

[0085] Raman R1 = A1 D / A1 G

[0086] In Equation 1, A1 D is the peak area of the absorption region (D band) from 1252 cm -1 to 1445 cm -1 in the Raman spectrum, and A1 G is the peak area of the absorption region (G band) from 1577 cm -1 to 1620 cm -1 in the Raman spectrum.

[0087] The Raman spectrum was measured using an InVia Raman microscope from Renishaw under the condition of 100% laser focusing level.

[0088] The analysis of the Raman spectrometer can be carried out under the following conditions: laser wavelength 532 nm, magnification x50, laser power 10%, 0.7 mV, laser exposure time 10 seconds. For example, after Raman tests are performed at multiple points (e.g., 3 or more, 5 or more, 10 or more, etc.) on the surface of the positive electrode active material layer 110, the average value can be used as the Raman R1 value of the corresponding positive electrode active material layer 110.

[0089] The positive electrode active material layer has the above Raman R1 value, so that the conductivity of the positive electrode active material layer 110 can be fully ensured, and the power characteristics of the secondary battery can be improved. In addition, the amorphous characteristics in the conductive material can be controlled, and the increase in resistance can be prevented.

[0090] Without being limited to a specific theory, but when carbon black or carbon nanotubes are used as the conductive material, the increase in resistance can be suppressed within the range of the above Raman R1 value, and uniform conductivity can be effectively achieved throughout the entire region of the positive electrode active material layer 110.

[0091] In some embodiments, the Raman R1 value of the positive electrode active material layer 110 can be in the range of 1.6 to 3.8, 2 to 3.5, or 2 to 3. By having the above Raman R1 value, the capacity characteristics and electrical characteristics can be improved while maintaining the appropriate amorphous characteristics of the conductive material.

[0092] In addition, without being limited to a specific theory, but by having the above Raman R1 value, the dispersion of the conductive material can be promoted to suppress the reduction of the pore characteristics in the positive electrode active material layer due to the excessive dispersion of too small conductive material particles. Therefore, the conductivity and the mobility of lithium ions can be balanced.

[0093] In some embodiments, when carbon black is used as the conductive material, carbon black with a Raman R2 value defined by Equation 2 in the range of 2.5 to 3.5 can be used. The Raman R2 value of Equation 2 can represent the intrinsic Raman R value of the conductive material.

[0094] Equation 2

[0095] Raman R2 = A2 D / A2 G

[0096] In Equation 2, A2 D is the peak area of the absorption region (D band) from 1252 cm -1 to 1445 cm -1 in the Raman spectrum, and A2 G is the peak area of the absorption region (G band) from 1577 cm -1 to 1620 cm -1 in the Raman spectrum.

[0097] The Raman spectrum was measured using an InVia Raman microscope from Renishaw at a laser focus level of 0%. The measurement conditions other than the focus level can be the same as those for measuring the Raman R1 value.

[0098] A laser focus level of 100% means setting the measurement area of a single shot or single scan of the Raman spectrometer to the maximum value. For example, a laser focus level of 0% means setting the measurement area of a single shot or single scan of the Raman spectrometer to the minimum value.

[0099] In one embodiment, carbon black with a Raman R2 value in the range of 2.5 to 3.3, 2.5 to 3.0, or 2.6 to 2.9 can be used.

[0100] In some embodiments, when carbon nanotubes are used as the conductive material, carbon nanotubes with a Raman R2 value defined by Equation 2 in the range of 1.8 to 2.8 can be used. In one embodiment, carbon nanotubes with a Raman R2 value of 1.8 to 2.5, 1.8 to 2.2, or 1.8 to 2.0 can be used.

[0101] In some embodiments, when graphite is used as the conductive material, graphite with a Raman R2 value defined by Equation 2 less than 1 can be used. In one embodiment, graphite with a Raman R2 value of 0.1 to 0.8, or 0.1 to 0.5 can be used.

[0102] By using the conductive material within the above Raman R2 value range, the Raman R1 value can be more effectively controlled within the above range, and the conductivity can be effectively controlled by the conductive material.

[0103] Based on the total weight of the positive electrode active material layer 110, the content of the positive electrode active material can be in the range of 90 wt% (weight percentage) to 98 wt%, the content of the binder can be in the range of 0.5 wt% to 5 wt%, and the content of the conductive material can be in the range of 0.5 wt% to 5 wt%.

[0104] Figure 2 and Figure 3 are schematic diagrams for describing the measurement of the Raman area ratio at a laser focusing level of 0% and a laser focusing level of 100%, respectively.

[0105] Reference Figure 2 , when the laser focusing level of the Raman spectrometer 50 is 0%, the minimum area MA1 that can be measured on the surface of the positive electrode active material layer 110 is set. In this case, the signal intensity obtained in the minimum area MA1 increases, and the characteristics of the local area can be measured more accurately and reliably.

[0106] However, if the distribution of the conductive material, the positive electrode active material, the binder, etc. in the positive electrode active material layer 110 is uneven, the measured values may deviate depending on the selected area. In addition, it may only reflect the characteristics of the selected area and cannot reflect the characteristics of the entire area of the positive electrode active material layer 110.

[0107] For example, when a large amount of conductive material and binder are locally included in the minimum area MA1, the signal from the active material may be affected by fluctuations or interference of the conductive material and binder components.

[0108] Reference Figure 3 , according to an embodiment of the present disclosure, when the laser focusing level of the Raman spectrometer 50 is 100%, the maximum area (MA2) that can be measured on the surface of the positive electrode active material layer 110 is set. Therefore, the composition and amount of the positive electrode active material layer 110 included in the measurable area increase, and a Raman value reflecting the compositional characteristics of the entire area of the positive electrode active material layer 110 can be obtained.

[0109] Therefore, the above Raman R1 value can reflect the amorphous / crystalline characteristics, the distribution of the conductive material, and the uniformity of the conductivity of the entire area of the positive electrode active material layer 110.

[0110] Therefore, it can be confirmed that by adjusting the Raman R1 value to the above range, the enhancement of capacity by introducing a high-nickel active material and the enhancement of conductivity by the conductive material can be uniformly achieved over the entire area of the positive electrode active material layer 110.

[0111] Figure 4 and Figure 5 are flowcharts for describing a method of manufacturing a positive electrode for a lithium secondary battery according to an embodiment of the present disclosure.

[0112] The positive electrode for the lithium secondary battery described above is not limited to the positive electrode manufactured by the following method. The following method is provided to describe an embodiment for more effectively obtaining the Raman R1 value.

[0113] Reference Figure 4 , in operations S10 and S20, an adhesive solution and a conductive material solution can be prepared respectively. The adhesive solution and the conductive material solution can be prepared independently.

[0114] For example, an organic adhesive (such as PVDF) can be mixed and stirred in an organic solvent (such as NMP) to prepare an adhesive solution.

[0115] In some embodiments, when forming the adhesive solution, the rotational speed of the stirrer can be in the range of 500 rpm to 2000 rpm, and the stirring time can be in the range of 1 hour to 5 hours. In one embodiment, the rotational speed can be adjusted in the range of 700 rpm to 1500 rpm, and the stirring time can be adjusted in the range of 2 hours to 4 hours.

[0116] The solid content of the adhesive solution can be in the range of 5 wt% to 20 wt%. In one embodiment, the solid content of the adhesive solution can be in the range of 7 wt% to 15 wt%, or 8 wt% to 12 wt%.

[0117] Within the above stirring conditions and solid content range, deviation of the Raman R1 value and reduction of local conductivity due to the carbon component of the adhesive can be prevented.

[0118] As described above, a conductive material (such as carbon black and / or carbon nanotubes) can be mixed in an organic solvent (such as NMP) to prepare a conductive material solution.

[0119] In some embodiments, the conductive material solution can be formed by mixing using a grinding device (such as a spike mill). When forming the conductive material solution, the linear speed of the spike mill can be adjusted in the range of 5 m / s to 15 m / s, and the flow rate can be adjusted in the range of 1 L / min to 5 L / min. In one embodiment, the linear speed of the spike mill can be adjusted in the range of 5 m / s to 12 m / s, and the flow rate can be adjusted in the range of 1 L / min to 2 L / min.

[0120] The solid content of the conductive material solution can be in the range of 4 wt% to 15 wt%. In one embodiment, the solid content of the conductive material solution can be in the range of 5 wt% to 15 wt%, 5 wt% to 12 wt%, or 5 wt% to 10 wt%.

[0121] In one embodiment, the solid content of the conductive material solution may be less than that of the binder solution. When the solid content of the conductive material solution is controlled to be less than that of the binder solution, improved and more uniform dispersion of the conductive material among the binder particles can be promoted.

[0122] In addition, under the above stirring conditions and within the range of the solid content, sufficient dispersibility of the conductive material can be obtained while easily achieving the Raman R1 value within the above range.

[0123] For example, in operation S30, a primary solution can be prepared by mixing (first mixing) the conductive material solution and the binder solution. A solvent (such as NMP) can be additionally added to prepare the primary solution.

[0124] The rotation speed of the stirrer used in the first mixing can be in the range of 1000 rpm to 2000 rpm, and the stirring time can be in the range of 20 minutes to 1 hour. In one embodiment, the rotation speed can be adjusted in the range of 1200 rpm to 1700 rpm, and the stirring time can be adjusted in the range of 20 minutes to 40 minutes.

[0125] For example, in operations S40 and S50, the positive electrode active material can be added to the primary solution for a second mixing to prepare the positive electrode paste.

[0126] The rotation speed of the stirrer used in the second mixing can be in the range of 1000 rpm to 2000 rpm, and the stirring time can be in the range of 1 hour to 5 hours. In one embodiment, the rotation speed can be adjusted in the range of 1200 rpm to 1700 rpm, and the stirring time can be adjusted in the range of 1.5 hours to 4 hours.

[0127] In one embodiment, the stirring time of the second mixing can be greater than that of the first mixing. Controlling the stirring time of the second mixing to be greater than that of the first mixing can improve the dispersibility of the positive electrode active material and promote the uniform dispersion of the conductive material among the positive electrode active materials.

[0128] In some embodiments, the solid content of the positive electrode paste can be in the range of 60 wt% to 80 wt%. In one embodiment, the solid content of the positive electrode paste can be in the range of 60 wt% to 75 wt%, or in the range of 60 wt% to 70 wt%. Within the above range, the viscosity and flow characteristics of the positive electrode paste can be adjusted to an appropriate range to prevent local distribution deviation of the conductive material and inhibit changes in the Raman R1 value during the drying and pressing processes.

[0129] After that, the positive electrode paste can be coated on the positive electrode current collector and then dried and pressed to obtain the positive electrode.

[0130] Reference Figure 5 , for example, in operation S10, an adhesive solution can be prepared. Then, for example, in operation S15, a conductive material can be added to the adhesive solution and then mixed to prepare a conductive material / adhesive solution. When preparing the conductive material / adhesive solution, a solvent (NMP) can be additionally added.

[0131] The same or similar stirring conditions as those Figure 4 used in operation S20 for preparing the conductive material solution can be used to prepare the conductive material / adhesive solution.

[0132] Then, in operation S25, an active material can be added to the conductive material / adhesive solution and mixed to prepare a positive electrode paste. The mixing can be carried out under conditions substantially the same as or similar to those Figure 4 of the second mixing in operation S40. The solid content of the positive electrode paste can be adjusted within a range substantially the same as or similar to the range Figure 4 described with reference to.

[0133] As described above, after the sufficient dispersion of the carbon-based material is achieved by pre-dispersing the adhesive solution and the conductive material solution, the positive electrode active material can be mixed. In addition, by using the above mixing conditions, the uniformity of the Raman characteristics and the conductive characteristics of the entire positive electrode active material layer can be obtained.

[0134] According to an embodiment of the present disclosure, the characteristics (such as Raman characteristics) of the positive electrode or the positive electrode active material layer do not necessarily depend on the above preparation methods and conditions. For example, the above Raman R1 value can also be changed by other factors, including the types of the positive electrode active material, the conductive material, and the adhesive, as well as their respective physical properties, the coating conditions of the positive electrode active material layer, etc.

[0135] Figure 6 and Figure 7 are a schematic plan view and a schematic cross-sectional view showing a lithium secondary battery according to an embodiment of the present disclosure. For example, Figure 7 is a cross-sectional view taken along the Figure 6 center line I-I' (in the thickness direction).

[0136] Reference Figure 6 and Figure 7 , the lithium secondary battery includes a positive electrode 100 and a negative electrode 130. The positive electrode 100 includes the positive electrode active material layer 110 and the positive electrode current collector 105 according to the embodiment of the present disclosure. The lithium secondary battery may further include a separator 140 disposed between the positive electrode 100 and the negative electrode 130.

[0137] The negative electrode 130 may include a negative electrode current collector 125 and a negative electrode active material layer 120 formed by coating a negative electrode active material on at least one surface of the negative electrode current collector 125.

[0138] Non-limiting examples of the negative electrode current collector 125 may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, etc. The thickness of the negative electrode current collector 125 may be, for example, in the range of 5 μm to 50 μm.

[0139] The negative electrode active material may be any material that is widely known in the art and can enable the insertion and extraction of lithium ions without particular limitation. For example, carbon-based materials (such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers, etc.), lithium metal, lithium alloys, silicon-containing materials, or tin-containing materials, etc. may be used.

[0140] Examples of amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0141] Examples of crystalline carbon may include graphite-based carbon, such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0142] Lithium metal may include pure lithium metal or lithium metal formed with a protective layer for inhibiting dendrite growth, etc. In one embodiment, a lithium metal-containing layer deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one embodiment, a lithium thin film layer may be used as the negative electrode active material layer.

[0143] Elements included in the lithium alloy may include, for example, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, indium, etc.

[0144] The silicon-containing material may provide capacity characteristics with further improved properties. The silicon-containing material may include Si, SiO x (0 < x < 2), SiO doped with a metal x (0 < x < 2), a silicon-carbon composite, etc. The metal may include lithium and / or magnesium, and SiO doped with a metal x (0 < x < 2) may include metal silicate.

[0145] In some embodiments, the negative electrode paste may be prepared by mixing the above negative electrode active material with a binder, a conductive material, and / or a dispersant, etc. in a solvent and stirring. The negative electrode paste may be coated on at least one surface of the negative electrode current collector, and then dried and pressed to prepare the negative electrode 130.

[0146] In the manufacture of the negative electrode, materials substantially the same as or similar to the binder and conductive material included in the positive electrode may also be used. In some embodiments, styrene-butadiene rubber (SBR)-based binders, carboxymethyl cellulose (CMC), polyacrylic acid-based binders, poly(3,4-ethylenedioxythiophene) (PEDOT)-based binders, etc. can be used as the negative electrode binder.

[0147] For example, the separator 140 may include a porous polymer film or a porous non-woven fabric. The porous polymer film may include polyolefin-based polymers such as ethylene polymers, propylene polymers, ethylene / butene copolymers, ethylene / hexene copolymers, ethylene / methacrylate copolymers, etc. The porous non-woven fabric may include, for example, high melting point glass fibers, polyethylene terephthalate fibers, etc.

[0148] The separator 140 may include a ceramic-based material. For example, inorganic particles may be coated on or dispersed in the polymer film to improve heat resistance.

[0149] In some embodiments, an electrode unit (electrode cell) is defined by the positive electrode 100, the negative electrode 130, and the separator 140, and a plurality of electrode units may be stacked to form an electrode assembly 150 having, for example, a jelly roll shape. For example, the electrode assembly 150 may be formed by winding, stacking, Z-folding, or stacking-folding of the positive electrode 100, the negative electrode 130, and the separator 140.

[0150] The electrode assembly 150 may be accommodated in a housing 160 together with an electrolytic solution to define a lithium secondary battery. In some embodiments, a non-aqueous electrolytic solution may be used as the electrolytic solution.

[0151] The non-aqueous electrolytic solution may include a lithium salt used as an electrolyte and an organic solvent. The lithium salt is represented, for example, as Li + X - , and examples of the anion X - may include F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N- 、(FSO2)2N - 、 CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - 、CF3(CF2)7SO3 - 、CF3CO2 - 、CF3CO2 - 、CH3CO2 - 、SCN - 、(CF3CF2SO2)2N - etc.

[0152] For example, the organic solvent may include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran, etc. These substances can be used alone or in combination of two or more.

[0153] In some embodiments, a solid electrolyte can be used instead of the above non-aqueous electrolyte. In this case, a lithium secondary battery can be manufactured in the form of an all-solid-state battery. In addition, a solid electrolyte layer can be provided between the positive electrode 100 and the negative electrode 130 instead of the above separator 140.

[0154] The solid electrolyte may include a sulfide-based electrolyte. Non-limiting examples of the sulfide-based electrolyte may include Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, Li2S-P2S5-LiCl-LiBr, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (where p and q are positive numbers, and M is P, Si, Ge, B, Al, Ga or In), Li7-xPS6-xCl x (0 ≤ x ≤ 2), Li7-xPS6-xBr x (0 ≤ x ≤ 2), Li7-xPS6-xI x (0 ≤ x ≤ 2), etc. These substances can be used alone or in combination of two or more.

[0155] In one embodiment, the solid electrolyte may include, for example, an oxide-based amorphous solid electrolyte such as Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, Li2O-B2O3-ZnO, etc.

[0156] As Figure 6 shown, the electrode tabs (the positive electrode tab and the negative electrode tab) may protrude from the positive electrode current collector 105 and the negative electrode current collector 125 included in each electrode unit to one end of the housing 160. The electrode tabs may be welded to one end of the housing 160 to be connected to the electrode leads (the positive electrode lead 107 and the negative electrode lead 127), and the electrode leads may extend or be exposed to the outside of the housing 160.

[0157] In Figure 6 it is shown that the positive electrode lead 107 and the negative electrode lead 127 protrude from the upper side of the housing 160 in the planar direction, but the position of the electrode leads is not limited to Figure 6 shown. For example, the electrode leads may protrude from at least one of the two side surfaces of the housing 160, and may also protrude from the lower side surface of the housing 160. Alternatively, the positive electrode lead 107 and the negative electrode lead 127 may be formed to protrude from different side surfaces of the housing 160.

[0158] A lithium secondary battery can be manufactured, for example, in a cylindrical, prismatic, pouch, or coin shape using a can.

[0159] Hereinafter, embodiments of the present disclosure will be described in more detail with reference to experimental examples. However, the following experimental examples are only for illustrating the embodiments of the present disclosure, and those skilled in the relevant technical field will understand that various changes and modifications can be made within the scope and technical concept of the present disclosure. These changes and modifications are appropriately included in the embodiments of the present disclosure. In addition, the embodiments can be combined into other embodiments.

[0160] Example 1

[0161] Manufacture of the positive electrode

[0162] 1) Preparation of the binder solution

[0163] PVDF powder was mixed with NMP solvent and stirred at a speed of 1000 rpm for 3 hours to prepare a binder solution with a solid content of 10 wt%.

[0164] 2) Preparation of the conductive material solution

[0165] Carbon black powder with a Raman R2 value of 2.8 was mixed in NMP solvent using a tip grinder at a linear speed of 8 m / s and a flow rate of 2 L / min to form a conductive material solution with a solid content of 6 wt%.

[0166] 3) Preparation of the positive electrode paste

[0167] LiNi 0.8 Mn 0.1 Co 0.1 O2 particles as the positive electrode active material were mixed with the binder solution and the conductive material solution to prepare a positive electrode paste with a solid content of 65 wt%. The weight ratio of the positive electrode active material, the conductive material (carbon black), and the binder (PVDF) was adjusted to 96.5∶2∶1.5.

[0168] Specifically, the conductive material solution and the binder solution were stirred (first mixing) with additional NMP solvent at a speed of 1500 rpm for 30 minutes to obtain a primary solution (also called the first solution).

[0169] After that, the positive electrode active material was added to the first solution and stirred (second mixing) at a speed of 1500 rpm for 2 hours to prepare the positive electrode paste.

[0170] The positive electrode paste was coated on aluminum foil, dried, and pressed to obtain the positive electrode.

[0171] Manufacture of the secondary battery

[0172] Prepare a negative electrode slurry containing 93 wt% natural graphite as the negative electrode active material, 5 wt% KS6 as the flake-type conductive material, 1 wt% styrene-butadiene rubber (SBR) as the binder, and 1 wt% carboxymethyl cellulose (CMC) as the thickener. KS6 is a conductive synthetic graphite that can be provided by TIMCAL, a subsidiary of Imerys Graphite & Carbon of Canada. Coat the negative electrode slurry on a copper substrate, dry and press it to prepare the negative electrode.

[0173] Slit the prepared positive electrode and negative electrode to a predetermined size, stack them with a separator (polyethylene, thickness: 15 μm) inserted therebetween to form an electrode unit, and then weld the tab portions of the positive electrode and the negative electrode. Put the welded positive electrode / separator / negative electrode assembly into a bag and seal the other three sides except for the electrolyte injection side. The area including the electrode tabs is included in the sealed portion.

[0174] Inject the electrolyte through the electrolyte injection side, seal the electrolyte injection side as well, and then impregnate for 12 hours or longer. After that, perform formation charging and discharging (charging conditions: CC-CV, 0.25C, 4.2V, 0.05C, cut-off; discharging conditions: CC, 0.25C, 2.5V, cut-off). The term "impregnation" used here refers to the process in which the electrolyte is absorbed and completely penetrates the positive electrode / separator / negative electrode assembly. After that, perform formation charging and discharging (charging conditions: CC-CV (constant current-constant voltage), 0.25C, 4.2V, 0.05C, cut-off; discharging conditions: CC, 0.25C, 2.5V, cut-off). More specifically, first charge the battery at a constant current until it reaches a constant voltage of 4.2V, and then the charging switches to the constant voltage mode while the current gradually decreases. The constant current rate is set to 0.25 times the battery capacity (C). 0.05C is the cut-off current, below which the charging process terminates. The battery discharges at a constant current of 0.25C, and 2.5V is the cut-off voltage, below which the discharging terminates. Charging and discharging can be repeated as needed.

[0175] When preparing the electrolyte, use an EC / EMC (volume ratio of 30 / 70) mixed solvent to prepare a 1M LiPF6 solution, and add 1 wt% ethylene carbonate (VC), 0.5 wt% 1,3-propensultone (PRS), and 0.5 wt% lithium bis(oxalato)borate (LiBOB) as the electrolyte.

[0176] Example 2

[0177] The positive electrode and the secondary battery were fabricated using the same method as in Example 1, except that carbon nanotubes (CNTs) (multi-walled carbon nanotubes with a Raman R2 of 1.9, i.e., MWCNTs) were used instead of carbon black as the conductive material, and the weight ratio of the positive electrode active material, conductive material, and binder in the positive electrode slurry was changed to 98:0.5:1.5.

[0178] Example 3

[0179] The positive electrode and the secondary battery were prepared using the same method as in Example 1, except that a mixture of carbon black and CNTs (the same CNTs as in Example 2) with a weight ratio of 1:1 was used as the conductive material, and the weight ratio of the positive electrode active material, CNTs, carbon black, and PVDF was adjusted to 97.5:0.5:0.5:1.5.

[0180] Example 4

[0181] The positive electrode and the secondary battery were prepared using the same method as in Example 1, except that when preparing the conductive material solution, the linear velocity of the tip grinder was changed to 10 m / s.

[0182] Example 5

[0183] The positive electrode and the secondary battery were prepared using the same method as in Example 1, except that when preparing the conductive material solution, the linear velocity of the tip grinder was changed to 6 m / s.

[0184] Example 6

[0185] The positive electrode and the secondary battery were prepared using the same method as in Example 1, except that when preparing the conductive material solution, the linear velocity of the tip grinder was changed to 10 m / s, and when preparing the positive electrode slurry, the stirring speeds of the first mixing and the second mixing were changed to 2000 rpm, respectively.

[0186] Example 7

[0187] The binder solution was prepared using the same method as in Example 1. The binder solution, the same carbon black as in Example 1, and NMP were mixed under the same tip grinder conditions as in Example 1 to prepare a conductive material / binder solution with a solid content of 6 wt%.

[0188] The same positive electrode active material as in Example 1 and additional NMP were mixed in the conductive material / binder solution and stirred at a speed of 1500 rpm for 2 hours to prepare a positive electrode slurry, which had the same solid content and weight ratio of the active material, conductive material, and binder as in Example 1.

[0189] Using the same method as in Example 1, a secondary battery was prepared using this positive electrode paste.

[0190] Comparative Example 1

[0191] The positive electrode active material and carbon black were added to the conductive material solution prepared in Example 1, and then stirred at a speed of 1500 rpm for 2 hours to prepare a positive electrode paste, which had the same solid content and weight ratio of active material, conductive material, and binder as in Example 1.

[0192] Using the same method as in Example 1, a secondary battery was prepared using this positive electrode paste.

[0193] Comparative Example 2

[0194] The conductive material solution and the binder solution were prepared using the same method as in Example 1.

[0195] The conductive material solution, the binder solution, and the same positive electrode active material as in Example 1 were mixed, and then stirred at a speed of 1500 rpm for 2 hours to prepare a positive electrode paste, which had the same solid content and weight ratio of active material, conductive material, and binder as in Example 1.

[0196] Using the same method as in Example 1, a secondary battery was prepared using this positive electrode paste.

[0197] Comparative Example 3

[0198] A positive electrode paste having the same solid content and weight ratio of active material, conductive material, and binder as in Example 1 was prepared, except that the flow rate in the tip grinder was changed to 0.5 L / min during the preparation of the conductive material solution.

[0199] Using the same method as in Example 1, a secondary battery was prepared using this positive electrode paste.

[0200] Comparative Example 4

[0201] The positive electrode and the secondary battery were prepared using the same method as in Example 1, except that the solid content of the conductive material solution was changed to 3 wt%.

[0202] Comparative Example 5

[0203] The positive electrode and the secondary battery were prepared using the same method as in Example 1, except that the solid content of the conductive material solution was changed to 18 wt%.

[0204] Comparative Example 6

[0205] The positive electrode and the secondary battery were prepared in the same manner as in Example 1, except that the solid content of the positive electrode paste was changed to 50 wt%.

[0206] Experimental Example

[0207] (1) Measurement of the Raman R1 value

[0208] Under the following conditions, after formation charging / discharging, the Raman R1 value defined by Equation 1 was measured from the surface of the positive electrode active material layer of the lithium secondary battery prepared as described above. Specifically, 3 regions on the surface of the positive electrode active material layer were selected, and the average value of the corresponding values was taken as the Raman R1 value.

[0209] i) Raman spectrometer: InVia Raman microscope, from Renishaw (UK)

[0210] ii) Laser focusing level: 100%

[0211] iii) Argon ion laser wavelength: 532 nm

[0212] iv) Exposure time: 10 seconds, mapping count: 10 times

[0213] v) Magnification: x50

[0214] vi) Laser power: 10%, 0.7 mV

[0215] vii) Grating: 1800 l / min

[0216] viii) Software: Resolutions Pro (data processing)

[0217] (2) DC-IR measurement

[0218] The lithium secondary batteries of each example and comparative example were discharged at a charge / discharge rate of 1C for 10 seconds at a state of charge (SOC) of 50%. The initial voltage and the end voltage were constructed as a linear equation, and the slope was used as the DC-IR.

[0219] (3) Evaluation of the 2C discharge capacity efficiency

[0220] The 2C discharge capacity efficiency was evaluated by calculating the ratio of the 2C discharge capacity to the 0.3C discharge capacity of the lithium secondary batteries of the examples and comparative examples as a percentage.

[0221] Table 1

[0222]

[0223] Referring to Table 1, in the examples within the range of the Raman R1 value satisfying the above, a low DC-IR value was obtained, and the conductivity and discharge efficiency were improved.

[0224] In the comparative examples, the same conductive material with the same Raman R2 value as in the examples was used. However, since the R1 value was less than 1.5 or greater than 4, local conductivity / resistance deviation of the positive electrode active material layer occurred, and thus both the DC-IR characteristics and the discharge efficiency decreased.

Claims

1. A positive electrode for a lithium secondary battery, comprising: Positive electrode current collector; and forming a positive electrode active material layer on the surface of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material and a conductive material, Wherein, the Raman R1 value expressed by Equation 1 measured on the surface of the positive electrode active material layer is in the range of 1.5 to 4.0: Equation 1 Raman R1=A1 D / A1 G Where, in equation 1, A1 D The Raman spectrum at 1252 cm was measured using an InVia Raman microscope from Renishaw at 100% laser focus level. -1 Up to 1445cm -1 The peak area of ​​the absorption region, A1 G The Raman spectrum at 1577 cm was measured using an InVia Raman microscope from Renishaw at 100% laser focus level. -1 Up to 1620cm -1 The peak area of ​​the absorption region.

2. The positive electrode for a lithium secondary battery according to claim 1, wherein The Raman R1 value is in the range of 1.6 to 3.

8.

3. The positive electrode for a lithium secondary battery according to claim 1, wherein The conductive material includes at least one of carbon black and carbon nanotubes.

4. The positive electrode for a lithium secondary battery according to claim 1, wherein The conductive material includes carbon black having a Raman R2 value in the range of 2.5 to 3.5 as defined by Equation 2: Equation 2 Raman R2=A2 D / A2 G Where, in equation 2, A2 D The Raman spectrum at 1252 cm was measured using an InVia Raman microscope from Renishaw at 0% laser focus level. -1 Up to 1445cm -1 The peak area of ​​the absorption region, A2 G The Raman spectrum at 1577 cm was measured using an InVia Raman microscope from Renishaw at 0% laser focus level. -1 Up to 1620cm -1 The peak area of ​​the absorption region.

5. The positive electrode for a lithium secondary battery according to claim 1, wherein The conductive material includes carbon nanotubes having a Raman R2 value in the range of 1.8 to 2.8 as defined by Equation 2: Equation 2 Raman R2=A2 D / A2 G Where, in equation 2, A2 D The Raman spectrum at 1252 cm was measured using an InVia Raman microscope from Renishaw at 0% laser focus level. -1 Up to 1445cm -1 The peak area of ​​the absorption region, A2 G The Raman spectrum at 1577 cm was measured using an InVia Raman microscope from Renishaw at 0% laser focus level. -1 Up to 1620cm -1 The peak area of ​​the absorption region.

6. The positive electrode for a lithium secondary battery according to claim 1, wherein The conductive material includes carbon black and carbon nanotubes.

7. The positive electrode for a lithium secondary battery according to claim 6, wherein: The mixing weight ratio of the carbon black to the carbon nanotubes is 3:7 to 7:

3.

8. The positive electrode for a lithium secondary battery according to claim 1, wherein The positive electrode active material includes lithium nickel metal oxide, the lithium nickel metal oxide further includes a cobalt element, and a molar ratio of cobalt in elements other than lithium and oxygen in the lithium nickel metal oxide is 0.1 or less.

9. The positive electrode for a lithium secondary battery according to claim 1, wherein The positive electrode active material includes a lithium nickel metal oxide in which a molar ratio of nickel among elements other than lithium and oxygen is 0.8 or more.

10. The positive electrode for a lithium secondary battery according to claim 1, wherein The positive electrode active material may be contained in an amount of 90 wt % to 98 wt % and the conductive material may be contained in an amount of 0.5 wt % to 5 wt % based on the total weight of the positive electrode active material layer.

11. A lithium secondary battery comprising: The positive electrode for a lithium secondary battery according to any one of claims 1 to 10; and A negative electrode opposite to the positive electrode.

12. A method for manufacturing a positive electrode for a lithium secondary battery, the method comprising: preparing a primary solution, wherein the primary solution is mixed with a positive electrode binder and a conductive material; preparing a positive electrode slurry by mixing a positive electrode active material into the primary solution; The positive electrode slurry is coated on a positive electrode current collector.

13. The method according to claim 12, wherein: The preparation of the primary solution comprises: preparing a positive electrode binder solution and a conductive material solution respectively; The positive electrode binder solution and the conductive material solution are mixed.

14. The method according to claim 13, wherein: The solid content of the conductive material solution is in the range of 4 wt % to 15 wt %.

15. The method according to claim 13, wherein: The solid content of the binder solution is in the range of 5 wt % to 20 wt %.

16. The method according to claim 12, wherein: The solid content of the positive electrode slurry is in the range of 60 wt % to 80 wt %.

17. The method according to claim 12, further comprising drying and pressing the coated positive electrode slurry to form a positive electrode active material layer, in, The Raman R1 value expressed by Equation 1 measured on the surface of the positive electrode active material layer is in the range of 1.5 to 4.0: Equation 1 Raman R1=A1 D / A1 G Where, in equation 1, A1 D The Raman spectrum at 1252 cm was measured using an InVia Raman microscope from Renishaw at 100% laser focus level. -1 Up to 1445cm -1 The peak area of ​​the absorption region, A1 G The Raman spectrum at 1577 cm was measured using an InVia Raman microscope from Renishaw at 100% laser focus level. -1 Up to 1620cm -1 The peak area of ​​the absorption region.

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