Positive electrode and secondary lithium battery including the same

Description

1 / 37 “POSITIVE ELECTRODE AND SECONDARY LITHIUM BATTERY INCLUDING THE SAME” TECHNICAL FIELD

[001] The present invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery including the same, and, more particularly, to a positive electrode exhibiting low porosity and high lamination density and a lithium secondary battery including the same. PREVIOUS TECHNIQUE

[002] Secondary lithium batteries are normally supplied with a positive electrode, a negative electrode, a separator and an electrolyte, and the positive and negative electrodes include active materials that allow the intercalation / deintercalation of lithium ions.

[003] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2, LiMnO4, or similar), lithium iron phosphate compound (LiFePO4), and similar compounds have been used as a positive electrode active material for secondary lithium batteries. Among those listed above, lithium cobalt oxide has high operating voltage and excellent capacity characteristics, but it is difficult to commercially apply lithium cobalt oxide in large-capacity batteries because cobalt, which is a raw material for lithium cobalt oxide, is expensive and of unstable supply. Lithium nickel oxide has low structural stability and therefore hardly has sufficient service life. Meanwhile, lithium manganese oxide has excellent stability but low capacity.Consequently, lithium-nickel based oxides, including at least two types of transition metals, have been developed to compensate for the limitations of lithium transition metal oxides, including Ni, Co or Mn in isolation, and, particularly, lithium-nickel-cobalt-manganese oxides, including Ni, Co and Mn, have been widely used in the field of batteries for electric vehicles. Petition 870250085567, dated 09 / 22 / 2025, p. 11 / 51 2 / 37

[004] Meanwhile, in addition to using a high-capacity positive electrode active material, materials included in the positive electrode are of vital importance for obtaining batteries with high energy density. To this end, research efforts are underway to make the most of the active material and make minimal use of conductive and binder material. In a typical example of using CNTs as a conductive material, the CNTs are positioned linearly between active materials, allowing easy conductivity to be achieved with a small amount, which maximizes the amount of charge from the active material.

[005] However, CNTs, under at least some pressure during electrode lamination, damage the active material, and reducing the lamination density to create space for linear CNTs between the active materials and thus avoid damage to the active material results in a thicker electrode with greater porosity, which makes it difficult to increase the energy density.

[006] Thus, research is needed to develop a positive electrode having reduced porosity and increased lamination density without causing damage to active materials. DISCLOSURE OF THE INVENTION TECHNICAL PROBLEM

[007] The present invention was designed to overcome the limitations described above and, therefore, one aspect of the present invention provides a positive electrode that exhibits excellent lamination density and low porosity by means of a combination of a single-particle type positive electrode active material and a point-type conductive material, such as carbon black, particularly a point-type conductive material having a large specific surface area and an excellent secondary structure.

[008] One aspect of the present invention also provides a secondary lithium battery exhibiting improved energy density, including the electrode Petition 870250085567, dated 09 / 22 / 2025, page 12 / 51 3 / 37 positive as described above. TECHNICAL SOLUTION

[009] [1] According to one aspect of the present invention, a positive electrode is provided having a positive electrode mixture layer, including a single-particle type positive electrode active material and a point type conductive material, arranged in a current collector, and having a lamination index of 0.01 to 1.00, as indicated by Equation 1 below. [Equation 1] RI = [(D50 / Dmean) X Bc] / (Sc X Oc) X 105

[010] In Equation 1 above, Dmean is a mean particle size (μm) of nodules measured from a scanning electron microscope image of the single-particle type positive electrode active material, D50 is a mean particle size (μm) in 50% cumulative volume in a particle size distribution plot obtained by a laser diffraction method for the single-particle type positive electrode active material, Bc is an apparent density of carbon black, given as a unitless number without a unit of apparent density of g / cm3, Sc is a BET specific surface area of ​​carbon black, given as a unitless number without a unit of specific surface area of ​​m2 / g, and Oc is an oil absorption number (OAN) of carbon black, given as a unitless number without a unit of oil absorption number of ml / 100 g.

[011] [2] The present invention provides the positive electrode according to [1] above, wherein the single-particle type positive electrode active material may have a D50 of 2.0 μm to 6.0 μm.

[012] [3] The present invention provides the positive electrode according to [1] and / or [2] above, wherein the single-particle type positive electrode active material may have a Dmean of 0.2 μm to 3.0 μm. Petition 870250085567, dated 09 / 22 / 2025, p. 13 / 51 4 / 37

[013] [4] The present invention provides the positive electrode according to at least one of [1] to [3] above, wherein the single-particle type positive electrode active material may have a D50 / Dmean of 1 to 10.

[014] [5] The present invention provides the positive electrode according to at least one of [1] to [4] above, wherein the point-type conductive material may have a specific surface area BET of 300 m2 / g up to 1300 m2 / g.

[015] [6] The present invention provides the positive electrode according to at least one of [1] to [5] above, wherein the point-type conductive material may have an oil absorption number of 250 ml / 100 g 500 ml / 100 g.

[016] [7] The present invention provides the positive electrode according to at least one of [1] to [6] above, wherein the point-type conductive material may have an apparent density of 0.05 cm3 / g 0.14 cm3 / g.

[017] [8] The present invention provides the positive electrode according to at least one of [1] to [7] above, wherein the single-particle type positive electrode active material may include at least one selected from the group consisting of a lithium nickel-based oxide and a lithium metal phosphate-based compound, the lithium nickel-based oxide may have a composition represented by Formula 1 below, and the lithium metal phosphate-based compound may have a composition represented by Formula 2 below. [Formula 1] Li1+xNiaCobM1cM2dO2-eXe

[018] In Formula 1 above, M1 includes at least one selection from Mn and Al, M2 includes at least one selection from the group consisting of W, Zr, Y, Ba, Ca, Ti, V, Mg, Ta and Nb, X includes at least one selection from the group consisting of N, P, S, F and Cl, ex, a, b, c, d and e satisfy 0 <x<0,1, 0,5<a<1, 0<b<0,35, 0<c<0,35, 0<d<0,05, e 0<e<0,05. Petition 870250085567, dated 09 / 22 / 2025, p. 14 / 51 5 / 37 [Formula 2] Li1+x[Fei-yMy]PO4

[019] In Formula 2 above, M includes at least one selected from the group consisting of Mn, Co, Ni, Al, Mg, and Ti, ex and y satisfy -0.5 <x<0,5 e 0<y<1.

[020] [9] The present invention provides the positive electrode according to at least one of [1] to [8] above, wherein the point-type conductive material may be carbon black.

[021]

[10] The present invention provides the positive electrode according to at least one of [1] to [9] above, wherein the positive electrode may have a porosity of 12.0% to 22.0%.

[022]

[11] The present invention provides the positive electrode according to at least one of [1] to

[10] above, wherein the single-particle type lithium-nickel-based oxide can be provided in an amount of 93.0% by weight to 99.0% by weight relative to the total weight of the positive electrode mixture layer.

[023]

[12] The present invention provides the positive electrode according to at least one of [1] to

[11] above, wherein the positive electrode mixing layer may further include a binder.

[024]

[13] According to another aspect of the present invention, a secondary lithium battery including the positive electrode is provided according to the present invention. ADVANTAGEOUS EFFECTS

[025] A positive electrode according to the present invention employs a combination of a single-particle type positive electrode active material in the form of a single particle and / or a nearly single particle having excellent particle resistance and a point-type conductive material having a large specific surface area and an excellent secondary structure, thus dispersing external force applied to the active material particles even during high-pressure lamination, Petition 870250085567, dated 09 / 22 / 2025, page 15 / 51 6 / 37 resulting in reduced particle breakage, crack formation, fine particles and porosity.

[026] In addition, a secondary lithium battery according to the present invention includes the positive electrode which has high lamination density and low porosity, as described above, and therefore has improved energy density and reduced cracking or breakage of active material particles, leading to reduced side reactions with an electrolyte, resulting in less gas generation and improved service life characteristics. METHOD OF CARRYING OUT THE INVENTION

[027] It will be understood that words or terms used in this document and in the claims of the present invention should not be interpreted as being limited to the meaning defined in commonly used dictionaries. It will further be understood that words or terms should be interpreted as having meanings that are consistent with the meanings in the context of the relevant art and technical idea of ​​the invention, based on the principle that an inventor can adequately define the meaning of words or terms to best explain the invention.

[028] Here, it will also be understood that the terms “include”, “comprise” or “have” specify the presence of characteristics, numbers, stages, elements or combinations thereof, but do not preclude the presence or addition of one or more other characteristics, numbers, stages, elements or combinations thereof.

[029] Here, the term “single particle type” is a particle type consisting of 30 nodules or less, and a single particle type encompasses a single particle consisting of a single nodule as well as a nearly single particle that is a compound of 2 to 30 nodules.

[030] The term “nodule” indicates a unitary body of lower particles that constitutes a single particle and a nearly single particle, and may be a single crystal. Petition 870250085567, dated 09 / 22 / 2025, page 16 / 51 7 / 37 without crystalline grain boundaries or it may be a polycrystal in which grain boundaries are not present when observed in a field of view of 5000* to 20000* using a scanning electron microscope.

[031] Here, the term “secondary particle” indicates a particle formed by the aggregation of a plurality of several dozen to several hundred primary particles. More specifically, the secondary particle is an aggregate of at least 50 primary particles.

[032] Here, when the term “particle” is described, any or all of a single particle, a nearly single particle, a primary particle, a node and a secondary particle may be included.

[033] Here, “Dmean” is calculated by taking an average value of the particle sizes of individual nodules in approximately 30 particles containing at least one nodule, as determined by scanning electron microscopy (SEM) of particles of positive electrode active material.

[034] Here, the term “D50” indicates a particle size relative to 50% of the volume-cumulative particle size distribution of the positive electrode active material powder. The average particle size D50 can be measured using a laser diffraction method. For example, the average particle size D50 can be measured by dispersing the positive electrode active material powder in a dispersion medium, introducing the dispersion medium into a commercial laser diffraction particle size measuring instrument (e.g., Microtrac MT 3000) and irradiating it with ultrasonic waves having a frequency of about 28 kHz and an output of 60 W to obtain a volume-cumulative particle size distribution plot, and calculating the particle size at 50% of the volume accumulation.

[035] Here, a “specific surface area (m2 / g)” is measured using a BET method and can specifically be calculated from a quantity of gas. Petition 870250085567, dated 09 / 22 / 2025, page 17 / 51 8 / 37 nitrogen adsorbed at a liquid nitrogen temperature (77 K) using BELSORP-mino II from BEL JAPAN, INC.

[036] Here, the term “apparent density (g / cm3)” indicates a mass (g)-volume (cm3) ratio of a point-type conductive material, measured without any external force applied.

[037] Here, the term “oil absorption number” of a point-type conductive material indicates a value determined by means of a method described in JIS K6221-B using DBP (dibutyl phthalate) as oil and converted to an equivalent value according to JIS K6217-4:2008 according to Equation (a). [Equation (a)] DBP absorption = (A-10.974) / 0.7833

[038] In Equation (a), A indicates a DBP absorption value measured using a method described in JIS K6221-B.

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

[040] A positive electrode and a secondary lithium battery according to the present invention may include at least one of the following components and may include any technically feasible combination of components from among the following components. Positive electrode

[041] A positive electrode according to the present invention has a positive electrode mixture layer, including a single-particle type active positive electrode material and a point type conductive material, arranged in a current collector, and having a lamination index of 0.01 to 1.00, as indicated by Equation 1 below. [Equation 1] RI = [(D50 / Dmean) X Bc] / (Sc X Oc) X 105

[042] In Equation 1 above, Dmean is an average particle size (μm) of Petition 870250085567, dated 09 / 22 / 2025, page 18 / 51 9 / 37 nodules measured from a scanning electron microscope image of the single-particle type positive electrode active material, D50 is a 50% cumulative volume average particle size in a particle size distribution plot obtained by a laser diffraction method for the single-particle type positive electrode active material, Bc is an apparent density of the point-type conductive material, given as a unitless number without a unit of apparent density in g / cm3, Sc is a BET specific surface area of ​​the point-type conductive material, given as a unitless number without a unit of specific surface area in m2 / g, and Oc is an oil absorption number (OAN) of the point-type conductive material, given as a unitless number without a unit of oil absorption number in ml / 100 g. Lamination index

[043] According to one embodiment of the present invention, the positive electrode has a layer of positive electrode mixture, including a single-particle type active positive electrode material and a point-type conductive material, arranged in a current collector, and has a lamination index of 0.01 to 1.00, as indicated by Equation 1 above. The lamination index is attributed to properties of the single-particle type active positive electrode material and the point-type conductive material included in the positive electrode and, in particular, attributed to factors affecting the lamination density and porosity of the positive electrode from the properties of each material.

[044] Specifically, to obtain a high-energy-density positive electrode, an increase in the amount of active material charge is usually applied, and typically carbon nanotubes, which provide conductivity even at low charges, have been used to reduce the amount of conductive material and increase the amount of active material. However, in this case, electrode thickness is difficult to control due to the length characteristics of Petition 870250085567, dated 09 / 22 / 2025, page 19 / 51 10 / 37 carbon nanotubes, and the increased lamination pressure inevitably damages the active material, resulting in a negligible improvement in energy density, even if a high-charge positive electrode is possible.

[045] However, according to one embodiment of the present invention, the positive electrode employs a combination of a single-particle or nearly single-particle type positive electrode active material and a point-type conductive material having a large specific surface area, and defines relationships between specific factors from the characteristics of each material, thus being obtainable as a positive electrode having improved energy density without damage to active material particles.

[046] Specifically, the rolling index is indicated by Equation 1 below and ranges from 0.01 to 1.00. [Equation 1] RI = [(D50 / Dmean) X Bc] / (Sc X Oc) X 105

[047] In Equation 1 above, Dmean is a mean particle size (μm) of nodules measured from a scanning electron microscope image of the single-particle type positive electrode active material, D50 is a mean particle size (μm) in 50% cumulative volume in a particle size distribution plot obtained by a laser diffraction method for the single-particle type positive electrode active material, Bc is an apparent density of the point-type conductive material, given as a unitless number without a unit of apparent density of g / cm3, Sc is a BET specific surface area of ​​the point-type conductive material, given as a unitless number without a unit of specific surface area of ​​m2 / g, and Oc is an oil absorption number (OAN) of the point-type conductive material, given as a unitless number without a unit of oil absorption number of ml / 100 g.

[048] D50 / Dmean included as a factor in the rolling index may be Petition 870250085567, dated 09 / 22 / 2025, page 20 / 51 11 / 37, termed the single-particle formation degree, indicates that the single-particle type particles of the positive electrode active material are not in the form of a secondary particle in which tens to hundreds of primary particles are aggregated. A lower ratio indicates that the positive electrode active material is more likely to be in a single-particle or near-single-particle form, and the increased particle strength allows the positive electrode active material to withstand higher rolling pressures without damage.

[049] Furthermore, the apparent density and oil absorption number of the point-type conductive material are properties related to a secondary structure of the point-type conductive material, where a lower apparent density indicates a more uniform and bulky structure, while a higher oil absorption number indicates a greater capacity to retain an electrolyte and a larger secondary structure. That is, the characteristics of the secondary structure of the point-type conductive material are ultimately a measure of how well the point-type conductive material is arranged between the particles of single-particle positive electrode active material to minimize porosity, and a lower apparent density and a higher oil absorption number indicate a better secondary structure of the point-type conductive material.

[050] Furthermore, the specific surface area of ​​the point-type conductive material can indicate the number of point-type conductive materials per unit mass, and a larger number of point-type conductive materials may indicate that point-type conductive materials can be arranged more effectively in the pores within the positive electrode.

[051] The lamination index according to one embodiment of the present invention is derived by considering the relationship of the factors as described above, and a greater number of point-type conductive materials per unit mass is beneficial for pore filling, but the fact that there are many materials Petition 870250085567, dated 09 / 22 / 2025, page 21 / 51 12 / 37 point-type conductors per unit mass can be indirectly attributed to a smaller secondary structure, and when the secondary structure of the point-type conductor material is, although bulky, not densely formed, the apparent density may be low, but the oil absorption number may also be low due to a reduced capacity to retain an electrolyte. That is, the present invention derives the lamination index by considering the characteristics of the point-type conductor material which has such a complex relationship.

[052] Furthermore, even when the point-type conductive material satisfies all the conditions and the relationships between them are well established, the use of an active material that hardly withstands high rolling pressure and is easily damaged can prevent obtaining a high energy density electrode and, therefore, the relationship was concluded by reflecting the particle size characteristics of an active material, i.e., the single-particle type positive electrode active material, in the rolling index.

[053] The rolling index determined by Equation 1 above can vary from 0.01 to 1.00, may preferably be 0.03 or more, 0.05 or more, 0.08 or more, 0.10 or more, 0.15 or more, or 0.20 or more, and may be 0.95 or less, 0.90 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.70 or less, 0.65 or less, or 0.60 or less.

[054] When the lamination index is less than 0.01, the secondary structure formed by the apparent density and oil absorption number of the point-type conducting material is very bulky and, therefore, the conducting material itself may have high porosity, may not be well arranged in the voids that may be formed in the positive electrode and, even when well arranged, may have a structure that hardly fills the micropores; therefore, the electrode porosity may not be reduced, which indicates that the energy density may not be improved. Furthermore, when the lamination index is greater than 1.00, the specific surface area Petition 870250085567, dated 09 / 22 / 2025, page 22 / 51 13 / 37 of the point-type conductive material is insufficient, hardly increasing the lamination density and therefore failing to reduce electrode porosity, and the conductive material particles may not be well arranged among the single-particle type positive electrode active material particles, hardly achieving conductivity. Furthermore, since the particle size characteristics of the positive electrode active material are closer to those of secondary particles than single particles, high lamination pressure can cause damage to the particles, leading to an increase in fine particles and a reduction in capacity.

[055] Next, each factor included in the rolling index relationship will be described. Active material for positive electrode

[056] According to one embodiment of the present invention, the single-particle type positive electrode active material may have a degree of single particle formation (D50 / Dmean) of 1 to 10. The single-particle type positive electrode active material has higher particle strength than typical secondary particle type positive electrode active materials, in which tens to hundreds of primary particles are aggregated, causing less particle breakage during lamination. Furthermore, since the single-particle type positive electrode active material has a small number of sub-parts (i.e., nodules) that constitute the particles, changes resulting from the expansion / contraction of primary particle volume during loading and unloading are small and, consequently, the generation of cracks within the particles is substantially reduced.

[057] A lower degree of single particle formation suggests that particles are more likely to be single particles or nearly single particles, consisting of a few nodules. Consequently, the degree of single particle formation may preferentially range from 1 to 8, 1 to 7, 1 to 6 or 1 to 5, and when the range Petition 870250085567, dated 09 / 22 / 2025, p. 23 / 51 If the 14 / 37 standard above is met, particle breakage can be reduced and lamination density can be improved, thus improving both service life characteristics and energy density.

[058] According to one embodiment of the present invention, the single-particle type positive electrode active material may have a D50 of 2.0 μm to 6.0 μm.

[059] The single-particle type positive electrode active material may have a 50% cumulative volume average particle size of 2.0 μm to 6.0 pm, preferably 2.3 pm or more, 2.5 pm or more, 2.7 pm or more, 3.0 pm or more, or 3.5 pm or more, and may be 6.0 pm or less, 5.8 pm or less, 5.5 pm or less, or 5.0 pm or less. When the D50 of the single-particle type positive electrode active material satisfies the above range, the lamination density may be increased without damage to the active material particles.

[060] According to one embodiment of the present invention, the single-particle type positive electrode active material nodule may have an average particle size (Dmean) of 0.2 pm to 3.0 pm, and the nodule may preferably have an average particle size of 0.5 pm or more, 0.7 pm or more, or 1.0 pm or more, and an average particle size of 2.8 pm or less, 2.5 pm or less, or 2.0 pm or less, and when the above range is satisfied, the degree range of single-particle formation may be satisfied and therefore an effect may be expected appropriately.

[061] The single-particle type positive electrode active material according to the present invention may include at least one selected from the group consisting of a lithium-nickel based oxide and a lithium metal phosphate based compound.

[062] For example, lithium nickel-based oxide may have a composition represented by Formula 1 below. Petition 870250085567, dated 09 / 22 / 2025, p. 24 / 51 15 / 37 [Formula 1] Lil+xNiaCObM1cM2dO2-eXe

[063] In Formula 1 above, M1 includes at least one selection from Mn and Al, M2 includes at least one selection from the group consisting of W, Zr, Y, Ba, Ca, Ti, V, Mg, Ta and Nb, X includes at least one selection from the group consisting of N, P, S, F and Cl, ex, a, b, c, d and e satisfy 0 <x<0,1, 0,5<a<1, 0<b<0,35, 0<c<0,35, 0<d<0,05, e 0<e<0,05.

[064] In Formula 1 above, M1 can be Mn, Al, or a combination thereof, preferably Mn or a combination of Mn and Al, and M2 can be at least one selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, preferably at least one selected from the group consisting of Zr, Y, Mg, and Ti, and more preferably Zr, Y, or a combination thereof. Although element M2 is not necessarily included, when an appropriate amount of element M2 is included, it can serve to promote grain growth during firing or increase the stability of a crystalline structure. Furthermore, X is an anion substituted for an oxygen site and can include N, P, S, F, or Cl.

[065] 1+x indicates a molar ratio of lithium in lithium-nickel oxide, ex can satisfy 0 <x<0,1, 0<x<0,08, 0<x<0,05, 0<x<0,03 ou 0<x<0,02.

[066] indicates a molar ratio of nickel among total metals, excluding lithium, in the nickel-lithium oxide, and may satisfy 0.50 <a<1,00, 0,60<a<0,99, 0,70<a<0,99 ou 0,75<a<0,99, 0,80<a<0,99, 0,82<a<0,99, 0,84<a<0,99 ou 0,86<a<0,99.

[067] b indicates a molar ratio of cobalt among total metals, excluding lithium, in lithium-nickel oxide and may satisfy 0 <b<0,35, 0,01<b<0,34, 0,01<b<0,30, 0,01<b<0,25, 0,01<b<0,20 ou 0,01<b<0,15.

[068] c indicates a molar ratio of M1 between total metals, excluding lithium, in lithium-nickel oxide, and may satisfy 0 <c<0,35, 0,01<c<0,34, 0,01<c<0,30, Petition 870250085567, dated 09 / 22 / 2025, p. 25 / 51 16 / 37 0.01 <c<0,25, 0,01<c<0,20 ou 0,01<c<0,15.

[069] d indicates a molar ratio of element M2 between total metals, excluding lithium, in lithium-nickel oxide and may satisfy 0 <d<0,05, 0<d<0,02 ou 0<d<0,01.

[070] and indicates a molar ratio of element X among the total nonmetals, excluding oxygen, in lithium-nickel oxide and may satisfy 0 <e<0,05, 0<e<0,02 ou 0<e<0,01.

[071] Meanwhile, lithium nickel-based oxide may further include a coating layer including at least one coating element selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si and S, on a particle surface.

[072] When a coating layer is provided on a single-particle type lithium-nickel-based oxide surface, the contact between an electrolyte and the single-particle type lithium-nickel-based oxide is suppressed by the coating layer, thus reducing transition metal elution or gas generation resulting from side reactions with the electrolyte.

[073] Preferably, the coating layer may include Co as a coating element. When a coating layer including Co is formed on a single-particle type lithium-nickel-based oxide particle surface, side reactions with an electrolyte can be suppressed and the output can be improved.

[074] In addition, the lithium metal phosphate-based compound may have a composition represented by Formula 2 below. [Formula 2] LÍ1+x[Fe1-yMy]PO4

[075] In Formula 2 above, M includes at least one selected from the group consisting of Mn, Co, Ni, Al, Mg, and Ti, ex and y satisfy -0.5 <x<0,5 e 0<y<1. Petition 870250085567, dated 09 / 22 / 2025, p. 26 / 51 17 / 37

[076] Lithium metal phosphate-based compound can be doped with M above. In this case, the lattice structure and the distance within the olivine crystal structure, which is a crystalline structure, are altered, leading to an increase in lithium ion diffusion and consequently improving the electrochemical characteristics of batteries, including the active positive electrode material.

[077] x can vary from -0.5 to 0.5, can preferably be -0.3 or more, 0.1 or more, or 0 or more, and can be 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[078] y can be 0 or more and less than 1, and can be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, 0.20 or less, 0.10 or less, or 0.05 or less.

[079] The lithium metal phosphate-based compound can be, for example, LiFePO4.

[080] The lithium metal phosphate-based compound according to the present invention may be in the form of a single particle consisting of only one primary particle, or in the form of an irregular secondary particle consisting of 2 to 50 primary particles. Furthermore, the lithium metal phosphate-based compound may include an olivine structure and, specifically, may be formed solely of an olivine structure. The coating layer according to the present invention may be formed not only on the secondary particle but also on the primary particle. That is, the coating layer according to the present invention may be uniformly present on a surface of the primary particle within the secondary particle.

[081] The coating layer may include a carbon coating layer having a graphite structure, and the coating layer may have a thickness of 0.5 nm to 5 nm. When the coating layer thickness is within the above range, the electrical conductivity is improved and also the ingress and Petition 870250085567, dated 09 / 22 / 2025, p. 27 / 51 18 / 37 lithium-ion output is not impaired. Specifically, the coating layer can have a thickness of 0.5 nm or more, 1.0 nm or more, 1.5 nm or more, 2.0 nm or more, 2.5 nm or more, or 3.0 nm or more, and a thickness of 5.0 nm or less.

[082] The coating layer can be applied uniformly over a surface of the lithium metal phosphate-based compound. That is, the coating layer can be in the form of a thin film. The coating layer can improve ionic conductivity and electronic conductivity during the charging and discharging of a battery, including a positive electrode active material. The coating layer may contain impurities such as nitrogen, oxygen and hydrogen in trace amounts, as well as carbon.

[083] The coating layer may be included in an amount of 0.5% by weight to 3% by weight relative to the total weight of the lithium metal phosphate-based compound, in order to improve electrical conductivity and not hinder the entry and exit of lithium ions. Point-type conductive material

[084] The positive electrode according to one embodiment of the present invention may include a point-type conductive material, and the point-type conductive material may include carbon black, and the carbon black may be, for example, at least one selected from the group consisting of acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black. In general, single-particle type positive electrode active materials use carbon nanotubes provided with high particle strength and conductivity that can be easily obtained even in a small quantity to increase the charge. However, carbon nanotubes are damaged under high rolling pressure, despite the strong particle strength as described above, and therefore are not suitable for the intended positive electrode to be obtained in the present invention. Petition 870250085567, dated 09 / 22 / 2025, page 28 / 51 19 / 37 Therefore, the positive electrode of the present invention may not include carbon nanotubes.

[085] According to one embodiment of the present invention, the point-type conductive material is a material that significantly affects the configuration of the lamination index ratio and, as described above, the specific surface area BET, the apparent density and the oil absorption number can be important factors.

[086] Point-type conductive material may have a BET specific surface area of ​​290 m2 / ga 1300 m2 / g measured by means of a BET method and may be specifically calculated from an amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77 K) using BELSORP-mino II from BEL JAPAN, INC. Preferably, the point-type conductive material may have a specific surface area BET of 300 m2 / g or more, 330 m2 / g or more, 370 m2 / g or more, 400 m2 / g or more, 420 m2 / g or more, 440 m2 / g or more, 460 m2 / g or more, 480 m2 / g or more, or 500 m2 / g or more, and also 1200 m2 / g or less, 1100 m2 / g or less, or 1000 m2 / g or less, 950 m2 / g or less, 900 m2 / g or less, or 880 m2 / g or less.

[087] Specific surface area is a factor that greatly affects the specification of the lamination index, and a larger specific surface area is preferable. Typically, a point-type conductive material having a specific surface area of ​​100 m² / g to 200 m² / g is applied, and a point-type conductive material having a specific surface area of ​​up to 250 m² / g is generally applied, and for applications requiring a high specific surface area conductive material, linear conductive materials such as carbon nanotubes are commonly used considering conductivity per unit mass. However, the lamination index according to one embodiment of the present invention is achievable only when a point-type conductive material having Petition 870250085567, dated 09 / 22 / 2025, page 29 / 51 20 / 37 a large specific surface area, not a linearly conductive material, is applied, and this can therefore be a factor that can minimize porosity in the positive electrode.

[088] Furthermore, the point-type conductive material may have an apparent density of 0.05 cm3 / g to 0.14 cm3 / g, and the apparent density indicates a mass (g)-volume (cm3) ratio of the point-type conductive material, measured without any external force applied. Preferably, the point-type conductive material may have an apparent density of 0.06 cm3 / g or more, 0.08 cm3 / g or more, 0.09 cm3 / g or more, or 0.10 cm3 / g or more, and also 0.135 cm3 / g or less, 0.132 cm3 / g or less, or 0.13 cm3 / g or less. When the apparent density satisfies the above range, the point-type conductive material is considered to have a secondary structure that may be positioned between active material particles, which may contribute to reducing porosity and increasing lamination density.

[089] Furthermore, the point-type conductive material may have an oil absorption number of 250 ml / 100 g 500 ml / 100 g, and the oil absorption number indicates a value determined by a method described in JIS K6221-B using DBP (dibutyl phthalate) as oil and converted to an equivalent value according to JIS K6217-4:2008 according to Equation (a). [Equation (a)] DBP absorption = (A-10.974) / 0.7833

[090] In Equation (a), A indicates a DBP absorption value measured using a method described in JIS K6221-B.

[091] The oil absorption number may preferably be 260 ml / 100 g or more, 270 ml / 100 g or more, 280 ml / 100 g or more, 290 ml / 100 g or more, or 300 ml / 100 g or more, and may be 495 ml / 100 g or less, 490 ml / 100 g or less, 485 ml / 100 g or less, or 480 ml / 100 g or less, and when the above ranges are met, conditions for a dense and bulky secondary structure can be achieved, which not only improves electrolyte retention but also Petition 870250085567, dated 09 / 22 / 2025, page 30 / 51 21 / 37 disperses external forces exerted on active material particles under high rolling pressure. Positive electrode composition

[092] The positive electrode according to the present invention may include a single-particle type positive electrode active material and a point type conductive material, as described above, and may further include a binder, and the positive electrode active material, the point type conductive material and the binder may form a positive electrode mixing layer, and the positive electrode mixing layer may be formed in a positive electrode current collector.

[093] In this case, the active positive electrode material may be included in an amount of 90% by weight to 99% by weight, more specifically 93% by weight or more, 95% by weight or more, 96% by weight or more, or 97% by weight or more, and 98.5% by weight or less, or 98% by weight or less, with respect to a total weight of the positive electrode mixture layer, and may exhibit excellent capacity characteristics when included in the above range.

[094] In addition, the point-type conductive material may be included in an amount of 0.1% by weight to 10% by weight, preferably 0.3% by weight or more, 0.5% by weight or more, 0.7% by weight or more, or 1.0% by weight or more, and also 9.0% by weight or less, 8.5% by weight or less, 8.0% by weight or less, 7.5% by weight or less, 7.0% by weight or less, or 6.5% by weight or less, with respect to the total weight of the positive electrode mixture layer.

[095] According to one embodiment of the present invention, the positive electrode may further include a binder. The binder serves to improve the bonding between particles of the positive electrode active material and the adhesion between the positive electrode active material and the current collector. Specific examples may include polyvinylidene fluoride (PVDF), a polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, Petition 870250085567, dated 09 / 22 / 2025, page 31 / 51 22 / 37 polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene-propylene-diene polymer (EPDM), a sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid and a polymer obtained by hydrogen substitution of the above materials with Li, Na or Ca, or various copolymers, and any one of them or a mixture of two or more of them may be used. The binder may be included in an amount of 0.1% by weight to 10% by weight, preferably 0.3% by weight or more, 0.5% by weight or more, 0.7% by weight or more, or 1.0% by weight or more, and also 9.0% by weight or less, 8.5% by weight or less, 8.0% by weight or less, 7.5% by weight or less, 7.0% by weight or less, or 6.5% by weight or less, with respect to the total weight of the positive electrode mixture layer.

[096] The positive electrode current collector may include a highly conductive metal and is not particularly limited, provided that the positive electrode mixture layer adheres readily to it and the positive electrode current collector has no reactivity in the voltage range of a battery. As the positive electrode current collector, for example, stainless steel, aluminum, nickel, titanium, heat-treated carbon, aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver or the like may be used. In addition, the positive electrode current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on a surface of the current collector to improve the adhesion of a positive electrode active material.For example, the positive electrode current collector can be used in various forms, such as a film, a sheet, a metal foil, a mesh, a porous body, a foam body, and a non-woven fabric body.

[097] The positive electrode can be prepared according to a typical method for preparing a positive electrode, except that the electrode active material powder Petition 870250085567, dated 09 / 22 / 2025, page 32 / 51 The 23 / 37 positive described above is used. Specifically, a positive electrode fluid paste composition prepared by dissolving or dispersing the positive electrode active material powder and, if necessary, optionally by dissolving or dispersing a binder, a conductive material and a dispersant in a solvent, is applied to the positive electrode current collector and then dried and laminated to prepare the positive electrode.

[098] The solvent may be a solvent commonly used in the technique and may be dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, water or the like, and any one of these or a mixture of two or more of these may be used. The amount of solvent to be used is sufficient if the solvent can dissolve or disperse the active material of the positive electrode, the conductive material, the binder and the dispersant, considering the application thickness of the fluid paste and the preparation yield, and subsequently have a viscosity that can provide excellent thickness uniformity in the application for the preparation of the positive electrode.

[099] Furthermore, in another method, the positive electrode can be prepared by molding the positive electrode fluid paste composition onto a separate support and then by laminating a film separate from the support onto the positive electrode current collector. Secondary lithium battery

[0100] Next, a secondary lithium battery according to the present invention will be described. A secondary lithium battery according to the present invention includes the positive electrode of the present invention described above.

[0101] Specifically, the secondary lithium battery includes a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive and negative electrodes, and an electrolyte. The positive electrode is the same as described above and therefore a detailed description of it. Petition 870250085567, dated 09 / 22 / 2025, page 33 / 51 24 / 37 will be omitted. Only the remaining components will be described in detail below.

[0102] In addition, the secondary lithium battery may selectively include a battery case to accommodate an electrode assembly consisting of the positive electrode, the negative electrode and the separator, and a sealing element to seal the battery case.

[0103] In a secondary lithium battery, the negative electrode may include a negative electrode current collector and a negative electrode mixing layer placed on the negative electrode current collector, and the negative electrode mixing layer may include a negative electrode active material, a binder, and a conductive material.

[0104] The negative electrode current collector is not particularly limited, provided it has high conductivity without causing chemical changes in the batteries. For example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel whose surface is treated with carbon, nickel, titanium, silver and the like, an aluminum-cadmium alloy and the like can be used.

[0105] The negative electrode current collector can typically have a thickness of 3 μm to 500 μm and preferably can have a thickness of 300 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less. The current collector may have fine irregularities formed on its surface to improve the bonding resistance with an active negative electrode material. For example, the current collector can be used in various forms, such as a film, a sheet, a metallic foil, a mesh, a porous body, a foam body, and a nonwoven fabric body.

[0106] A compound capable of reversibly intercalating and deintercalating lithium can be used as a negative electrode active material, and examples of this may be a carbonaceous material, such as artificial graphite, natural graphite, Kish graphite, Petition 870250085567, dated 09 / 22 / 2025, page 34 / 51 25 / 37 pyrolytic carbon, mesocarbon microspheres, mesophase pitches, cokes derived from petroleum tar or coal pitch, mesophase pitch-based carbon fiber, graphite-based carbon fiber, amorphous carbon, soft carbon or hard carbon; a lithium-alloyable (semi)metallic material, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy or Al alloy; a lithium-doped and dedoped (semi)metallic oxide material, such as SiOb (0 <b<2), SnO2, óxido de vanádio e óxido de vanádio e lítio; um material compósito heterogêneo, tal como compósito de Si-C ou compósito de Sn-C; ou um filme fino de metal-lítio, e qualquer um deles ou uma mistura de dois ou mais deles pode ser usado.

[0107] Preferably, the negative electrode active material may include at least one selected from the group consisting of a silicon-based active material, a carbon-based active material and a silicon-carbon composite active material and, more preferably, the carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, soft carbon and hard carbon, the silicon-based active material may include pure Si and / or SiOb particles (0 <b<2), e o material ativo de compósito de silício-carbono pode incluir um compósito de Si-C. Além disso, o material ativo de eletrodo negativo pode ser um material ativo misto no qual dois ou mais dos materiais descritos acima são misturados.

[0108] The active negative electrode material may be included in an amount of 60% by weight to 99% by weight, preferably 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more and even 98% by weight or less, 97% by weight or less or 95% by weight or less, relative to the total weight of the negative electrode mixture layer.

[0109] The binder is a component to aid in the bonding between a conductive material, an active material and a current collector, and can typically be added in an amount of 0.1% by weight to 10% by weight relative to a Petition 870250085567, dated 09 / 22 / 2025, page 35 / 51 26 / 37 total weight of the negative electrode mixing layer, and may be included in an amount of 0.2% by weight or more, 0.3% by weight or more, or 0.5% by weight or more, and even 8% by weight or less, or 5% by weight or less. Examples of binders may include at least one selected from the group consisting of styrene-butadiene copolymer, acrylated styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic rubber, butyl rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylenepropylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, and polyvinyl alcohol.Specifically, examples of the binder may include at least one selected from the group consisting of styrene-butadiene copolymer, acrylated styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene styrene copolymer, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, diacetylcellulose, cellulose butylate acetate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethylcellulose and cyanoethylsucrose. Preferably, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose or a mixture thereof is desirable.The conductive material is a component to further improve the conductivity of the negative electrode active material and may be included in an amount of 10% by weight or less, preferably 5% by weight or less, 3% by weight or less, 2% by weight or less, or 1% by weight or less, and also 0.01% by weight or more, 0.05% by weight or more, 0.08% by weight or more, 0.1% by weight or more, or 0.3% by weight or more, relative to the total weight of the negative electrode mixture layer. This conductive material is not particularly limited, provided it has conductivity without causing chemical changes in the battery and, for example, a conductive material such as graphite. Petition 870250085567, dated 09 / 22 / 2025, page 36 / 51 27 / 37 such as natural graphite and artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lamp black and thermal black; conductive fibers, such as carbon-based fibers and metal-based fibers; carbon fluoride; metal powder, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxide, such as titanium oxide; or polyphenylene derivatives, or the like, may be used.

[0110] The negative electrode mixing layer can be prepared by applying a negative electrode fluid paste composition, which is prepared by dissolving or dispersing a negative electrode active material and, optionally, a binder and a conductive material in a solvent, onto a negative electrode current collector and drying the resulting product, or it can be prepared by molding the negative electrode fluid paste composition onto a separate support and then laminating a film separate from the support onto the negative electrode current collector.

[0111] In a lithium secondary battery, a separator serves to separate the negative and positive electrodes and provide a path for lithium ion movement. Any separator can be used without specific limitation, provided it is normally used as a separator in a lithium secondary battery. In particular, a separator having high moisture retention capacity for an electrolyte, as well as low resistance to the movement of electrolytic ions, is preferable. Specifically, a porous polymer film, for example, a porous polymer film prepared using a polyolefin-based polymer, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure having two or more layers thereof, can be used. Additionally, a typical porous nonwoven fabric, for example, Petition 870250085567, dated 09 / 22 / 2025, page 37 / 51 28 / 37 For example, a nonwoven fabric made of glass fiber having a high melting point or polyethylene terephthalate fiber can be used. Additionally, a coated separator including a ceramic component or a polymeric material can be used to ensure heat resistance or mechanical strength, and a separator having a single-layer structure or a multi-layer structure can optionally be used.

[0112] The electrolyte used in the present invention may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten-type inorganic electrolyte and the like, all of which may be used in the preparation of a secondary lithium battery, but without limitation.

[0113] The electrolyte may include an organic solvent and a lithium salt.

[0114] Any organic solvent may be used without specific limitation, provided it can serve as a medium through which ions involved in an electrochemical reaction of a battery can move.Specifically, as an organic solvent, an ester-based solvent, such as methyl acetate, ethyl acetate, γ-butyrolactone and ε-caprolactone; an ether-based solvent, such as dibutyl ether or tetrahydrofuran; a ketone-based solvent, such as cyclohexanone; an aromatic hydrocarbon-based solvent, such as benzene and fluorobenzene; a carbonate-based solvent, such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC); an alcohol-based solvent, such as ethyl alcohol and isopropyl alcohol; nitriles, such as R-CN (where R is a linear, branched or cyclic C2 to C20 hydrocarbon group and may include an aromatic double-bonded ring or ether linkage); amides such as dimethylformamide; Dioxolanes, such as 1,3-dioxolane, or sulfolanes can be used.Among these solvents, a carbonate-based solvent is preferable, and a mixture of a cyclic carbonate (for example, Petition 870250085567, dated 09 / 22 / 2025, pp. 38 / 51 29 / 37 ethylene carbonate or propylene carbonate) having a high ionic conductivity and a high dielectric constant and a linear carbonate-based compound having a low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate), the mixture that can increase the charge / discharge performance of a battery is more preferable.

[0115] Any compound can be used as the lithium salt without specific limitation, as long as it can supply lithium ions used in a secondary lithium battery. To be specific, a lithium salt anion may be at least one selected from the group consisting of F-, Cl-, Br-, I-, NO3-, N(CN)2-, BF4-, CF3CF2SO3, (CF3SO2)2N-, (FSO2)2N-, CF3CF2(CF3)2CO-, (CF3SO2)2CH-, (SF5)3C-, (CF3SO2)3C-, CF3(CF2)7SO3-, CF3CO2-, CH3CO2-, SCN-, and (CF3CF2SO2)2N-, and as lithium salt, LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlU4, LiAlCk, UCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, Lil or LiB(C2O4)2 can be used. The lithium salt can preferably be used in a concentration range of 0.1 M to 2.0 M. When the lithium salt concentration is within the above range, the electrolyte has adequate conductivity and viscosity and can therefore exhibit excellent performance, and lithium ions can move effectively.

[0116] In the electrolyte, to improve the service life properties of a battery, suppress battery capacity decline and improve battery discharge capacity, one or more types of additives, for example, a haloalkylene carbonate-based compound, such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide, a nitrobenzene derivative, sulfur, a quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, an ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride and the like may be additionally included. In this case, the additive may be included in an amount of 0.1% by weight to 5% by weight relative to the total weight of the electrolyte. Petition 870250085567, dated 09 / 22 / 2025, pp. 39 / 51 30 / 37 EXAMPLES

[0117] Examples of the present invention will be described in detail below in such a way that they can be easily carried out by a person skilled in the art to which the present invention relates. The present invention can, however, be embodied in many different forms and is not limited to the examples presented here.

[0118] Examples 1 to 6 and Comparative Examples 1 to 5.

[0119] A single-particle lithium-nickel oxide having particle size characteristics as described in Table 1, which had a composition of LiNi0.6Co0.1Mn0.3O2, was used as a positive electrode active material and carbon black having the characteristics described in Table 1 below was used to prepare positive electrodes of Examples 1 to 6 and Comparative Examples 1 to 5.

[0120] The active positive electrode material, carbon black, and a PVDF binder were mixed in an N-methylpyrrolidone solvent in a weight ratio of 97.0:1.2:1.8 to prepare a fluid positive electrode paste (5,000 mPa.s), and the fluid paste was applied to the surface of an aluminum current collector, dried at 130 °C and rolled at a contact pressure of 2,000 kgf / cm to prepare positive electrodes. [Table 1] Active material of positive electrode D50 Active material of positive electrode Dmean Carbon black Apparent density Carbon black BET Carbon black OAN Lamination index Example 1 3.91 2.05 0.12 299 314 0.244 Example 2 3.91 2.05 0.11 302 320 0.217 Example 3 3.91 2.05 0.14 590 211 0.214 Example 4 3.91 2.05 0.12 867 252 0.105 Example 5 3.91 2.05 0.13 1078 272 0.085 Example 6 3.91 2.05 0.12 1284 336 0.053 Comparative Example 1 3.91 2.05 0.09 58 202 1.465 Petition 870250085567, dated 09 / 22 / 2025, pages 40 / 51 31 / 37 Comparative Example 2 3.91 2.05 0.13 122 183 1.111 Comparative Example 3 3.91 2.05 0.15 39 140 5.240 Comparative Example 4 3.91 2.05 0.02 1310 486 0.006 Comparative Example 5 3.91 2.05 0.01 800 362 0.007

[0121] Examples 7 to 10 and Comparative Examples 6 to 8

[0122] A single-particle lithium iron phosphate having particle size characteristics as described in Table 2, which had a composition of LiFePO4, was used as a positive electrode active material and carbon black having the characteristics described in Table 2 below was used to prepare positive electrodes of Examples 7 to 10 and Comparative Examples 6 to 8.

[0123] The active positive electrode material, carbon black, and a PVDF binder were mixed in an N-methylpyrrolidone solvent in a weight ratio of 97.0:1.2:1.8 to prepare a fluid positive electrode paste (approximately 15,000 mPa.s), and the fluid paste was applied to the surface of an aluminum current collector, dried at 130 °C, and rolled at a contact pressure of 2,000 kgf / cm² to prepare positive electrodes. ________[Table 2] Active material of positive electrode D50 Active material of positive electrode Dmean Carbon black Apparent density Carbon black BET Carbon black OAN Lamination index Example 7 1.1 0.2 0.11 302 320 0.626 Example 8 1.1 0.2 0.14 590 211 0.619 Example 9 1.1 0.2 0.12 867 252 0.302 Example 10 1.1 0.2 0.13 1078 272 0.244 Comparative Example 6 1.1 0.2 0.09 58 202 4.225 Comparative Example 7 1.1 0.2 0.13 122 183 3.203 Comparative Example 8 1.1 0.2 0.15 39 140 15,110

[0124] Particle size characteristics of the electrode active material Petition 870250085567, dated 09 / 22 / 2025, pages 41 / 51 Positive 32 / 37 carbon black and physical properties were measured using the following methods.

[0125] 1) Dmean(μm) is calculated by taking an average value of the particle sizes of individual nodules in approximately 30 particles containing at least one nodule, as captured by scanning electron microscopy (SEM) at 5.0 K magnification for particles of positive electrode active material.

[0126] 2) D50 (μm) was measured by dispersing the active material powder from the positive electrode in a dispersion medium. The dispersion medium was introduced into a laser diffraction particle size measuring instrument (Microtrac MT 3000) and irradiated with ultrasonic waves having a frequency of approximately 28 kHz and an output of 60 W to obtain a volume-cumulative particle size distribution graph, and the particle size at 50% of the volume accumulation was calculated.

[0127] 3) Specific surface area (m2 / g) was measured using a BET method and was calculated from an amount of nitrogen gas adsorbed at a liquid nitrogen temperature (77 K) using BELSORP-mino II from BEL JAPAN, INC.

[0128] 4) Apparent density (g / cm3) indicates a mass (g)-volume (cm3) ratio of a point-type conductive material and was measured without any external force applied.

[0129] 5) The oil absorption number was derived as a value determined by a method described in JIS K6221-B using DBP (dibutyl phthalate) as oil and converted to an equivalent value according to JIS K6217-4:2008 according to Equation (a) below. [Equation (a)] DBP absorption = (A-10.974) / 0.7833

[0130] In Equation (a), A indicates a DBP absorption value measured by Petition 870250085567, dated 09 / 22 / 2025, pages 42 / 51 33 / 37 by means of a method described in JIS K6221-B. Experimental Example 1: Evaluation of electrode characteristics (porosity and lamination density)

[0131] The lamination density was measured for a mixed powder of the positive electrode active material and carbon black from the Examples and Comparative Examples using a density measuring device (Caver Pellet Press). Specifically, 3 g of a mixed powder of the positive electrode active material and carbon black from the Examples and Comparative Examples were divided into small portions and packed in a cylindrical holder having a diameter of 13 mm and then compressed under a pressure of 9 tonf to measure the lamination density (g / cc).

[0132] Porosity was calculated using Mathematical Equation 1 below. [Mathematical Equation 1] Porosity of the positive electrode mixing layer after lamination (%) = {1-(density of the positive electrode mixing layer after lamination / actual density of the positive electrode mixing layer)} X 100

[0133] In Equation 1 above, the actual density of the positive electrode mixture layer is the density of a positive electrode mixture layer measured when the positive electrode mixture layer is brought to a predetermined size and pressed with press equipment until changes in the thickness of the positive electrode mixture layer stop, and the electrode density of the positive electrode mixture layer after lamination is the density of a positive electrode mixture layer measured when the positive electrode mixture layer is brought to a predetermined size after lamination. [Table 3] Porosity (%) Lamination density (g / cc) Example 1 20.2 3.57 Example 2 20.7 3.55 Example 3 19.3 3.61 Example 4 18.6 3.65 Petition 870250085567, dated 09 / 22 / 2025, pp. 43 / 51 34 / 37 Example 5 18.0 3.67 Example 6 17.4 3.70 Comparative Example 1 25.3 3.34 Comparative Example 2 27.2 3.26 Comparative Example 3 26.6 3.29 Comparative Example 4 26.0 3.31 Comparative Example 5 25.5 3.34 [Table 4] Porosity (%) Lamination density (g / cc) Example 7 19.1 2.54 Example 8 18.9 2.51 Example 9 19.5 2.59 Example 10 19.3 2.57 Comparative Example 6 24.1 2.35 Comparative Example 7 23.9 2.31 Comparative Example 8 23.7 2.33

[0134] Referring to Table 3 above, it is determined that Examples 1 to 6 which satisfy the lamination index exhibited excellent lamination density, and carbon black was well disposed in the pores between particles of positive electrode active material and therefore the porosity was also achieved at a considerably low level.

[0135] Meanwhile, it was determined that, in Comparative Examples 1 to 5, where the lamination index was less than 0.01 or greater than 1.00, carbon black properties were not appropriate in relation to positive electrode active material particles, i.e., specific surface area, OAN and apparent density did not form an appropriate relationship and therefore the lamination density was assessed as low and the porosity was assessed as high.

[0136] Referring to Table 4 above, it is determined that, similarly to the results in Table 3 above, Examples 7 to 10 showed low porosity and high lamination density compared to Comparative Examples 6 to 8. Experimental Example 2: Battery Performance Evaluation

[0137] A porous polyethylene separator was placed between the electrode Petition 870250085567, dated 09 / 22 / 2025, pages 44 / 51 35 / 37 positive and negative electrodes from Examples and Comparative Examples were used to prepare an electrode array, and the array was placed inside a battery box. Afterward, an electrolyte solution was injected to prepare a secondary lithium battery.

[0138] In this case, the electrolytic solution was prepared by dissolving 1 M LiPF6 in an organic solvent with a volume ratio of ethylene carbonate / ethylmethyl carbonate / diethyl carbonate of 3:4:4, and the negative electrode was prepared as follows.

[0139] The negative electrode was prepared by adding artificial graphite as a graphite-based active material, carbon black as a conductive material, and CMC:SBR as a binder to distilled water in a weight ratio of 95.6:1.0:1.1:2.3 to prepare a fluid negative electrode paste having a solids content concentration of 45% by weight, and in this case, the conductive material and binder were dispersed in water using a homogeneous mixer at 2,500 rpm for 30 minutes, and then the negative electrode active material was added and dispersed at 2,500 rpm for 30 minutes to prepare the fluid negative electrode paste.

[0140] The fluid negative electrode paste was applied to a copper current collector (thickness: 8 μm) with a charge quantity of 10.0 mg / cm2, as a negative electrode current collector, and then pressed by lamination and dried in a vacuum oven at 130 °C for 10 hours to prepare a negative electrode.

[0141] The secondary lithium battery was charged to 4.2 V at a C-rate of 0.1 C and then discharged to 2.5 V to perform an activation process.

[0142] Each secondary lithium battery prepared above was charged to 4.25 V in CCCV mode at 0.2 C (final current: 1 / 20 C). After that, the secondary lithium battery was charged to 4.25 V at a constant current of 0.33 C at 45 Petition 870250085567, dated 09 / 22 / 2025, pp. 45 / 51 A charge was heated to 36 / 37 °C and discharged to 2.5 V at a constant current of 0.33 C, which was defined as one cycle, and the charge capacity and discharge capacity were measured during 100 charge-discharge cycles. Using the measurement results, the capacity retention was calculated as follows and shown in Tables 5 and 6 below.

[0143] Capacity retention (%): = (discharge capacity after 100 cycles / discharge capacity after 1 cycle) * 100 [Table 5] Capacity Retention (%) Example 1 95.1 Example 2 94.3 Example 3 95.7 Example 4 94.3 Example 5 93.8 Example 6 93.1 Comparative Example 1 84.4 Comparative Example 2 80.5 Comparative Example 3 81.7 Comparative Example 4 88.8 Comparative Example 5 86.9 [Table 6] Capacity Retention (%) Example 7 92.5 Example 8 92.2 Example 9 91.8 Example 10 92.4 Comparative Example 6 87.9 Comparative Example 7 87.2 Comparative Example 8 87.8

[0144] Referring to Table 5 above, it is determined that Examples 1 to 6 that satisfy the lamination index exhibited excellent service life characteristics because collateral reactions caused by the breakage of active material particles were significantly reduced, despite the reduced porosity, leading to increased energy density.

[0145] However, it can be understood that Comparative Examples 1 to 3, which have a high lamination index, have a relatively smaller number of Petition 870250085567, dated 09 / 22 / 2025, pp. 46 / 51 37 / 37 conductive materials than the Examples, indicating fewer conductive paths formed, and it can be understood that Comparative Examples 4 and 5, which have a low lamination index, have relatively longer conductive paths than the Examples due to an increase in electrode porosity caused by the failure to reduce the porosity of the conductive material itself and micropores in the electrode. Consequently, Comparative Examples with shorter or longer conductive paths than the Examples may exhibit faster battery degradation, as evidenced by lower capacity retention.

[0146] Furthermore, referring to Table 6 above, it can be seen that the results show the same trend as those presented in Table 5 for both the Examples and the Comparative Examples.

[0147] That is, when a positive electrode is prepared by applying a positive electrode active material and a conductive material so that the lamination index according to an embodiment of the present invention is satisfied, it is determined that the porosity of the electrode can be reduced and the lamination pressing can be carried out under a high lamination density, and thus a short and dense conductive path is formed, thereby improving service life characteristics and, consequently, it is expected that the battery output can also be improved due to enhanced resistance characteristics of the electrode. Petition 870250085567, dated 09 / 22 / 2025, pp. 47 / 51

Claims

1 / 3 CLAIMS 1. Positive electrode having a positive electrode mixture layer, CHARACTERIZED in that it comprises a single-particle type positive electrode active material and a point-type conductive material, arranged in a current collector, and having a lamination index of 0.01 to 1.00, indicated by Equation 1 below: [Equation 1] RI = [(D50 / Dmean) X Bc] / (Sc X Oc) X 105 wherein, in Equation 1 above, Dmean is a mean particle size (μm) of nodules measured from a scanning electron microscope image of the single-particle type positive electrode active material, D50 is a mean particle size (μm) in 50% cumulative volume in a particle size distribution plot obtained by a laser diffraction method for the single-particle type positive electrode active material, Bc is a density apparent point-type conductive material,Given as a unitless number without a unit of apparent density in g / cm3, Sc is a BET specific surface area of ​​the point-type conductive material, given as a unitless number without a unit of specific surface area in m2 / g, and Oc is an oil absorption number (OAN) of the point-type conductive material, given as a unitless number without a unit of oil absorption number in ml / 100 g.

2. Positive electrode, according to claim 1, CHARACTERIZED in that the active material of the single-particle type positive electrode has a D50 of 2.0 μm to 6.0 μm. Petition 870250085567, dated 09 / 22 / 2025, pp. 48 / 51 2 / 3 3. Positive electrode, according to claim 1, CHARACTERIZED in that the active material of the single-particle type positive electrode has a Dmean of 0.2 μm to 3.0 μm.

4. Positive electrode, according to claim 1, CHARACTERIZED in that the active material of the single-particle type positive electrode has a D50 / Dmean of 1 to 10.

5. Positive electrode, according to claim 1, CHARACTERIZED in that the point-type conductive material has a specific surface area BET of 290 m2 / ga 1300 m2 / g.

6. Positive electrode, according to claim 1, CHARACTERIZED in that the point-type conductive material has an oil absorption number of 250 ml / 100 g 500 ml / 100 g.

7. Positive electrode, according to claim 1, CHARACTERIZED in that the point-type conductive material has an apparent density of 0.05 cm3 / g 0.14 cm3 / g.

8. Positive electrode, according to claim 1, CHARACTERIZED in that the active material of the single-particle type positive electrode comprises at least one selected from the group consisting of a lithium-nickel based oxide and a lithium metal phosphate based compound, the lithium-nickel based oxide having a composition represented by Formula 1 below, and the lithium metal phosphate based compound having a composition represented by Formula 2 below: [Formula 1] Li1+xNiaCobM1cM2dO2-eXe wherein, in Formula 1 above, M1 comprises at least one selected from Mn and Al, M2 comprises at least one selected from the group consisting of W, Petition 870250085567, dated 22 / 09 / 2025, p.49 / 51 3 / 3 Zr, Y, Ba, Ca, Ti, V, Mg, Ta and Nb, X comprises at least one selected from the group consisting of N, P, S, F and Cl, ex, a, b, c, d and e satisfy 0 <x<0,1, 0,5<a<1, 0<b<0,35, 0<c<0,35, 0<d<0,05, e 0<e<0,05, e [Fórmula 2] LÍl+x[Fei-yMy]PO4 em que, na Fórmula 2 acima, M compreende pelo menos um selecionado do grupo que consiste em Mn, Co, Ni, Al, Mg e Ti, e x e y satisfazem -0,5<x<0,5 e 0<y<1.

9. Positive electrode, according to claim 1, CHARACTERIZED in that the point-type conductive material comprises carbon black.

10. Positive electrode, according to claim 1, CHARACTERIZED in that the positive electrode has a porosity of 12.0% to 22.0%.

11. Positive electrode, according to claim 1, CHARACTERIZED in that the single-particle type lithium-nickel oxide-based material is provided in an amount of 93.0% by weight to 99.0% by weight relative to the total weight of the positive electrode mixture layer.

12. Positive electrode, according to claim 1, CHARACTERIZED in that the positive electrode mixing layer further comprises a binder.

13. Secondary lithium battery, CHARACTERIZED in that it comprises the positive electrode as defined in claim 1. Petition 870250085567, dated 09 / 22 / 2025, pp. 50 / 51