Cathode material powder, cathode containing the same, and lithium secondary battery

Abstract

The positive electrode material powder according to the present invention is a positive electrode material powder containing a positive electrode active material including lithium nickel-based oxide particles in which the content of Ni among all metals excluding lithium is 50 mol% to 80 mol%. The lithium nickel-based oxide particles are in the form of pseudo single particles composed of one single nodule or a composite of 30 or less nodules, and satisfy a PCF value represented by the following formula (1) of 2.0 or more and 3.4 or less. Formula (1): PCF = S BET ×P0×(D 50 -D min ) / (D max -D 50 (In formula (1), S BET is the BET specific surface area of the positive electrode material powder (unit: m 2 / g), P0 is the intensity (vol%) of the maximum peak in the volume cumulative particle size distribution measured for the positive electrode material powder using the laser diffraction method, D 50 is the particle size when the volume cumulative amount in the volume cumulative particle size distribution of the positive electrode material powder is 50%, D min is the minimum particle size in the volume cumulative particle size distribution of the positive electrode material powder, and D max is the maximum particle size in the volume cumulative particle size distribution of the positive electrode material powder.)

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0092287 dated July 17, 2023, Korean Patent Application No. 10-2023-0098548 dated July 27, 2023, Korean Patent Application No. 10-2024-0094050 dated July 16, 2024, and Korean Patent Application No. 10-2024-0094051 dated July 16, 2024, all of which are incorporated herein by reference.

[0002] The present invention relates to a positive electrode material powder, a positive electrode containing the same, and a lithium secondary battery, and more particularly to a positive electrode material powder that has excellent continuous charging characteristics and generates little fine powder during electrode manufacturing, a positive electrode containing the same, and a lithium secondary battery. [Background technology]

[0003] Generally, a lithium secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte, and the positive electrode and negative electrode contain an active material that allows for the insertion and deintercalation of lithium ions.

[0004] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMnO4, etc.), and lithium iron phosphate (LiFePO4) have been used as positive electrode active materials for lithium secondary batteries. Among these, lithium cobalt oxide has the advantage of a high operating voltage and excellent capacity characteristics, but the high price of cobalt, the raw material, and its unstable supply make it difficult to commercially apply to high-capacity batteries. Lithium nickel oxide has poor structural stability, making it difficult to achieve sufficient lifespan characteristics. On the other hand, lithium manganese oxide has excellent stability but poor capacity characteristics. Therefore, lithium composite transition metal oxides containing two or more transition metals have been developed to complement the problems of lithium transition metal oxides containing Ni, Co, or Mn alone, and among these, lithium nickel cobalt manganese oxide (hereinafter simply referred to as "NCM-based lithium composite transition metal oxide") containing Ni, Co, and Mn is widely used in the field of electric vehicle batteries.

[0005] On the other hand, conventionally developed NCM-based lithium composite transition metal oxides generally consist of spherical secondary particles formed by the aggregation of tens to hundreds of primary particles. However, when using NCM-based lithium composite transition metal oxides in this form of secondary particles, particle cracking, where primary particles fall off during the rolling process in cathode manufacturing, is likely to occur, and cracks can develop inside the particles during the charge-discharge process. When particle cracking or cracking occurs in the cathode active material, the contact area with the electrolyte increases, leading to increased gas generation due to side reactions with the electrolyte and increased degradation of the active material, resulting in a decrease in lifespan characteristics.

[0006] To solve these problems, a technique has been proposed to increase the firing temperature during the production of NCM-based lithium composite transition metal oxides, thereby producing single-particle cathode active materials instead of secondary particles. In the case of single-particle cathode active materials, the contact area with the electrolyte is smaller compared to conventional secondary-particle cathode active materials, resulting in fewer side reactions with the electrolyte, superior particle strength, and less particle cracking during electrode manufacturing. Therefore, applying single-particle cathode active materials offers the advantage of superior gas generation and lifespan characteristics.

[0007] However, in the case of single-particulate cathode active materials, there are fewer interfaces between primary particles that serve as pathways for lithium ion movement within the particle, resulting in reduced lithium mobility and a decrease in capacity characteristics compared to the case of secondary-particulate cathode active materials.

[0008] One strategy to increase the capacity of single-particulate positive electrode active material is to increase the drive voltage. However, with NCM-based lithium composite transition metal oxides, when the drive voltage exceeds 4.3V, especially 4.35V, side reactions with the electrolyte become vigorous, leading to the dissolution of transition metal ions and a rapid decrease in battery performance due to phase transitions in the crystal structure.

[0009] In particular, the main reason why side reactions with the electrolyte become more severe at high voltages of 4.35V or higher is that fine powder generation increases due to particle breakage during electrode manufacturing, but conventional single-particulate positive electrode active materials alone cannot sufficiently suppress the generation of fine powder. Therefore, there is a need to develop a cathode material powder that can be driven stably at high voltage, generates little fine powder during rolling, and achieves excellent continuous charging characteristics. [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] One objective of the present invention is to solve the above-mentioned problems and to provide a cathode material powder that controls the powder properties of the cathode material powder and generates less fine powder during rolling. Another object of the present invention is to provide a positive electrode containing the above-described positive electrode material powder and a lithium secondary battery.

Means for Solving the Problems

[0011] In one aspect, the present invention provides a positive electrode material powder containing a positive electrode active material containing lithium nickel-based oxide particles in which the content of Ni among all metals excluding lithium is 50 mol% to 80 mol%. The lithium nickel-based oxide particles are in the form of pseudo single particles composed of one single nodule or a composite of 30 nodules or less, and satisfy a PCF value represented by the following formula (1) of 2.0 or more and 3.4 or less.

[0012] Formula (1): particle cracking factor(PCF)=S BET ×P0×(D 50 -D min ) / (D max -D 50 )

[0013] In the above formula (1), S BET is the BET specific surface area (unit: m 2 / g) of the positive electrode material powder, P0 is the intensity (intensity of max peak, vol%) of the maximum peak in the volume cumulative particle size distribution measured for the positive electrode material powder using the laser diffraction method, D 50 is the particle size when the volume cumulative amount in the volume cumulative particle size distribution of the positive electrode material powder is 50%, D min is the minimum particle size in the volume cumulative particle size distribution of the positive electrode material powder, and D max is the maximum particle size in the volume cumulative particle size distribution of the positive electrode material powder.

[0014] The lithium nickel-based oxide particles may be represented by the following [Chemical Formula 1].

[0015] [Chemical Formula 1] Li a Ni b Co cMn d M 1 e O2

[0016] In the above chemical formula 1, M 1 may be one or more elements selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, with 0.8 ≤ a ≤ 1.2, 0.5 ≤ b ≤ 0.8, 0 <c≦0.3、0<d≦0.4、0≦e≦0.2であってもよい。

[0017] The aforementioned cathode material powder has a BET specific surface area of ​​0.2 m². 2 / g or more 1.3m 2 It may be less than / g. The positive electrode material powder may have a P0 of 8 or higher. D of the aforementioned positive electrode material powder 50 The particle size may be between 1 μm and 10 μm.

[0018] D of the aforementioned positive electrode material powder min The particle size may be between 0.75 μm and 2.0 μm. D of the aforementioned positive electrode material powder max The particle size may be between 8 μm and 18 μm. The positive electrode material powder may have an SP value of 0.20 or more and 0.33 or less, as represented by the following formula (2).

[0019] Formula (2): SP=(D 50 -D min ) / (D max -D 50 )

[0020] The PCF value of the positive electrode material powder may be 2.5 or more and 3.2 or less. When the positive electrode material powder is pressurized at 9 tons, the generation rate of fine particles with a particle size of 1 μm or less may be 3% by volume or less.

[0021] In another embodiment, the present invention provides a positive electrode comprising the positive electrode material powder described above. In another embodiment, the present invention provides a lithium secondary battery comprising the positive electrode, the negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. The lithium secondary battery may have a charging termination voltage of 4.35V or higher during operation. [Effects of the Invention]

[0022] The positive electrode material powder according to the present invention is characterized in that the PCF value satisfies the range of the present invention. A positive electrode using positive electrode material powder whose PCF falls outside the range of the present invention cannot have a suitable BET specific surface area and a suitable volume cumulative particle size distribution particle size value for the positive electrode active material, resulting in increased particle cracking during positive electrode rolling, more severe side reactions with the electrolyte during high-voltage driving, and reduced continuous charging characteristics. In contrast, positive electrode material powder whose PCF satisfies the range of the present invention exhibits less particle cracking during positive electrode rolling, thereby reducing side reactions with the electrolyte during high-voltage driving and showing excellent continuous charging characteristics. [Brief explanation of the drawing]

[0023] [Figure 1] This graph shows the volume-cumulative particle size distribution (PSD) of the cathode material powder produced by Example 1, as measured by Experimental Examples 1 and 2. [Figure 2] This graph shows the volume cumulative particle size distribution (PSD) of the cathode material powder produced by Comparative Example 2, as measured in Experimental Examples 1 and 2. [Figure 3] This graph shows the evaluation results of leakage current during continuous charging, as shown in Experiment Example 3. [Figure 4] This graph shows only the current in the graph in Figure 3. [Figure 5] This graph shows only the voltages in the graph in Figure 3. [Modes for carrying out the invention]

[0024] The terms and words used in this specification and in the claims are not to be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0025] In this invention, "single particle" refers to a particle consisting of one single nodule. In this invention, "pseudo-single particle" refers to a composite particle consisting of 30 or fewer nodules.

[0026] In the present invention, "nodule" means a particle unit body that constitutes a single particle or a pseudo-single particle. The nodule may be a single crystal lacking crystalline grain boundaries, or a polycrystalline material in which no grain boundaries are visible when observed with a scanning electron microscope (SEM) at a field of view of 5,000 to 20,000 times. The average particle size of the nodule can be measured as the arithmetic mean of the particle sizes of each nodule measured using a scanning electron microscope (SEM).

[0027] In this invention, "secondary particle" refers to a particle formed by the aggregation of several tens to hundreds of primary particles. More specifically, a secondary particle is an aggregate of 40 or more primary particles.

[0028] The term "particle" as used in this invention may include one or all of the following: single particles, pseudo-single particles, primary particles, nodules, and secondary particles.

[0029] In this invention, the "specific surface area" is measured by the BET method, and specifically, it can be calculated from the amount of nitrogen gas adsorbed at liquid nitrogen temperature (77K) using the BELSORP-mini II manufactured by BEL Japan.

[0030] In the present invention, "P0", "D min "D 50 ", and "D max " is the particle size value of the volume cumulative particle size distribution of the positive electrode active material powder measured using the laser diffraction method. Specifically, P0 is the intensity of the maximum peak (vol%) appearing in the volume cumulative particle size distribution of the positive electrode active material powder, and D min D is the smallest particle size that appears in the volume cumulative particle size distribution of the positive electrode active material powder. 50 D is the particle size when the volume cumulative amount appearing in the volume cumulative particle size distribution of the positive electrode active material powder is 50%, and max This is the maximum particle size that appears in the volume-cumulative particle size distribution of the positive electrode active material powder. The particle size value of the volume-cumulative particle size distribution can be measured, for example, by dispersing the positive electrode active material powder in a dispersion medium, introducing it into a commercially available laser diffraction particle size analyzer (e.g., Microtrac MT 3000), irradiating it with ultrasound at approximately 28 kHz at an output of 60 W, and then obtaining a graph of the volume-cumulative particle size distribution.

[0031] The inventors of this invention conducted extensive research to develop a positive electrode material powder for lithium secondary batteries that exhibits minimal particle cracking during electrode rolling and superior continuous charging characteristics. As a result, they discovered that when the powder properties of the positive electrode material powder satisfy a specific relationship, particle cracking during rolling is reduced, side reactions with the electrolyte are minimized, and excellent battery characteristics can be achieved at high voltages. This led to the completion of the present invention.

[0032] Cathode material powder The cathode material powder according to the present invention will be described below. Specifically, the cathode material powder according to the present invention is a cathode material powder containing a cathode active material which includes lithium nickel-based oxide particles having a Ni content of 50 mol% to 80 mol% among all metals excluding lithium, wherein the lithium nickel-based oxide particles are in the form of single particles consisting of one single nodule or pseudo-single particles which are composites of 30 or fewer nodules, and the cathode material powder satisfies a PCF value of 2.0 or more and 3.4 or less, which is represented by the following formula (1).

[0033] Formula (1): particle cracking factor(PCF)=S BET ×P0×(D 50 -D min ) / (D max -D 50 )

[0034] In formula (1) above, S BET This is the BET specific surface area (unit: m²) of the positive electrode material powder. 2 P0 is the intensity of the maximum peak (vol%) in the volume cumulative particle size distribution of the positive electrode material powder measured using laser diffraction, and D 50 This is the particle size when the volume cumulative amount in the volume cumulative particle size distribution of the positive electrode material powder is 50%, and D min This is the minimum particle size in the volume cumulative particle size distribution of the positive electrode material powder, and D max This is the maximum particle size in the volume cumulative particle size distribution of the positive electrode material powder.

[0035] Conventionally, single-particle lithium nickel oxide particles used as cathode material powders had the advantage of minimal particle cracking during rolling. However, when driven at high voltage, the particle cracking during rolling was not small enough to sufficiently suppress side reactions with the electrolyte.

[0036] As a result of extensive research to solve these problems, the inventors of the present invention have discovered that by controlling the PCF value of the positive electrode material powder within a certain range, particle cracking during positive electrode rolling can be reduced, the resulting side reactions with the electrolyte can be decreased, and continuous charging characteristics can be improved, thus completing the present invention.

[0037] The PCF value is a combination of the BET specific surface area of ​​the cathode material powder and the particle size value of the volume cumulative particle size distribution of the cathode material powder measured using the laser diffraction method. In order to achieve the excellent effects intended by the present invention, a suitable combination of the BET specific surface area of ​​the cathode material powder and the particle size value is required.

[0038] In detail, even if the BET specific surface area of ​​the cathode material powder meets a certain range, if the particle size value is not adjusted to meet the PCF range, particle cracking cannot be properly prevented during rolling. Conversely, even if the particle size value meets a certain range, if the BET specific surface area of ​​the cathode material powder is not adjusted to meet the PCF range, particle cracking cannot be properly prevented during rolling.

[0039] More specifically, the PCF is determined by the volume cumulative particle size distribution of the positive electrode material powder measured using laser diffraction, and the P0 and D min , D 50 , D max , and S, which is the BET specific surface area of ​​the positive electrode material powder. BET (Unit: m) 2 The PCF is a parameter consisting of / g) and is expressed as shown in formula (1) above. The PCF may be 2.0 or more and 3.4 or less, preferably 2.15 or more and 3.35 or less, more preferably 2.4 or more and 3.3 or less, and even more preferably 2.5 or more and 3.2 or less. If the PCF value is less than 2.0, S BET The PCF is excessively low, or the volume-cumulative particle size distribution is excessively wide from left to right, or the particle size distribution of large particles formed by the aggregation of multiple single particles or pseudo-single particles is excessively wide. In such a state, the probability of particle cracking occurring due to rolling of large particles formed by the aggregation of multiple single particles or pseudo-single particles is high, and therefore, side reactions between the positive electrode active material and the electrolyte increase during continuous charging. If the PCF value exceeds 3.4, S BETThe PCF is either excessively high, the volume-cumulative particle size distribution is excessively narrow from left to right, or the particle size distribution of single or pseudo-single particles is excessively wide. In such conditions, friction between particles becomes severe during electrode rolling, reducing rolling characteristics and increasing particle cracking due to rolling. In particular, even if a coating layer is formed to suppress side reactions with the electrolyte and stabilize the surface of the positive electrode active material, if particle cracking occurs, a new unstable surface is formed, which is a problem. When an unstable surface is newly formed as described above, side reactions between the positive electrode active material and the electrolyte increase, which reduces the battery life and continuous charging characteristics. Therefore, when the PCF satisfies the above range, particle cracking of 1 μm or less is reduced during electrode rolling, side reactions with the electrolyte are reduced, and the life characteristics and continuous charging characteristics are improved.

[0040] On the other hand, the BET specific surface area value and particle size value of the cathode material powder that satisfy the aforementioned PCF range may be controlled by various methods, but preferably by controlling the Ni content contained in the lithium nickel oxide particles, the composition of the lithium nickel oxide particles, the temperature and time conditions during firing of the cathode active material precursor and lithium source, the firing temperature and firing time during the formation of the coating layer formed on the cathode active material, and the grinding conditions of the cathode material powder.

[0041] Furthermore, the positive electrode active material particles of the present invention may be single particles consisting of one nodule, and / or pseudo-single particles which are composites of 30 or fewer nodules, preferably 2 to 20, more preferably 2 to 10, or may be in a form containing these. Preferably, the positive electrode material powder according to the present invention may consist of a combination of single particles and pseudo-single particle-like positive electrode active material particles. This is because if the number of nodules constituting the positive electrode active material particles exceeds 30, particle cracking increases during electrode manufacturing, internal crack generation increases due to expansion / contraction of nodule volume during charging and discharging, and the improvement effect on high-temperature lifetime characteristics and high-temperature storage characteristics may decrease.

[0042] On the one hand, the lithium nickel-based oxide particles may have a composition represented by the following [Chemical Formula 1].

[0043] [Chemical Formula 1] Li a Ni b Co c Mn d M 1 e O2

[0044] In the above Chemical Formula 1, M 1 is one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and 0.8 ≦ a ≦ 1.2, 0.5 ≦ b ≦ 0.8, 0 < c ≦ 0.3, 0 < d ≦ 0.3, 0 ≦ e ≦ 0.2 may be satisfied. When the molar ratio of lithium satisfies the above range, a stable layered crystal structure can be formed.

[0045] The above a represents the molar ratio of lithium in the lithium composite transition metal oxide particles, and 0.8 ≦ a ≦ 1.2, 0.9 ≦ a ≦ 1.1, or 0.95 ≦ a ≦ 1.10 may be satisfied. When the molar ratio of lithium satisfies the above range, a stable layered crystal structure can be formed.

[0046] The above b represents the molar ratio of nickel among all the metals excluding lithium in the lithium composite transition metal oxide particles, and 0.5 ≦ b ≦ 0.8, 0.50 ≦ b ≦ 0.75, 0.55 ≦ b ≦ 0.70, or 0.55 ≦ b ≦ 0.65 may be satisfied. Since the higher the content of nickel among the transition metals, the higher the capacity can be realized, it is more advantageous for realizing high capacity that the content of nickel is 0.5 or more.

[0047] The above c represents the molar ratio of cobalt among all the metals excluding lithium in the lithium nickel-based oxide, and 0 < c ≦ 0.3, 0 < c ≦ 0.25, 0 < c ≦ 0.2, 0 < c ≦ 0.15, or 0 < c ≦ 0.1 may be satisfied. When the molar ratio of cobalt satisfies the above range, good resistance characteristics and output characteristics can be realized.

[0048] Said d represents the molar ratio of manganese among all the metals excluding lithium in the lithium nickel-based oxide, and may be 0 < d ≤ 0.4, 0.1 ≤ d ≤ 0.4, 0.15 ≤ d ≤ 0.4, or 0.2 < d ≤ 0.4. When the molar ratio of manganese satisfies the above range, the structural stability of the positive electrode active material can be shown to be good.

[0049] Said e represents the molar ratio of element M among all the metals excluding lithium in the lithium nickel-based oxide 1 where said M 1 is a doping element substituted at the transition metal site, and may be 0 ≤ e ≤ 0.20, 0 ≤ e ≤ 0.15, or 0 ≤ e ≤ 0.10. When M 1 is contained in a suitable amount, it can play a role in promoting particle growth during firing or improving the stability of the crystal structure.

[0050] On the other hand, the positive electrode material powder has a BET specific surface area of 0.2 m 2 / g or more and 1.3 m 2 / g or less, preferably 0.3 m 2 / g or more and 1.0 m 2 / g or less, more preferably 0.4 m 2 / g or more and 0.9 m 2 / g or less, even more preferably 0.5 m 2 / g or more and 0.85 m 2 / g or less. When the positive electrode material powder satisfies the above BET specific surface area range, the rolling characteristics of the electrode can be improved, particle cracking can be reduced, and side reactions with the electrolytic solution can be suppressed.

[0051] On the other hand, said P0 is the intensity (intensity of max peak, vol%) of the maximum peak in the volume cumulative particle size distribution measured for the positive electrode material powder using the laser diffraction method, and said P0 may be 8 or more, preferably 9 or more, more preferably 10 or more. When P0 satisfies the above range, it can have a suitable form of volume cumulative particle size distribution, so particle cracking is reduced and a suitable electrode density can be obtained.

[0052] On the other hand, D 50 This is the average particle size in the volume cumulative particle size distribution measured using the laser diffraction method for the cathode material powder, and D 50 The particle size may be 1 μm or more and 10 μm or less, preferably 2 μm or more and 8 μm or less, more preferably 3 μm or more and 7 μm or less, and even more preferably 3 μm or more and 5 μm or less. When the above range is met, the processability during electrode manufacturing can be improved, the electrochemical properties can be increased due to high electrolyte impregnation, the resistance can be reduced, and the output characteristics can be improved.

[0053] On the other hand, D min This is the minimum particle size in the volume cumulative particle size distribution measured using the laser diffraction method for the cathode material powder, and D min The thickness may be 0.75 μm or more and 2.0 μm or less, preferably 0.8 μm or more and 1.5 μm or less, and more preferably 0.9 μm or more and 1.4 μm or less. The D min When the above range is met, the friction between particles is not large, so rolling properties can be excellent, the gaps between large particles can be effectively filled by small particles, resulting in excellent electrode density, and particle cracking is reduced, which reduces side reactions between the positive electrode active material and the electrolyte.

[0054] On the other hand, D max This is the maximum particle size in the volume cumulative particle size distribution measured using the laser diffraction method for the cathode material powder, and D max The thickness may be 8 μm or more and 18 μm or less, preferably 9 μm or more and 16 μm or less, and more preferably 10 μm or more and 14 μm or less. The above D max When the above range is met, a suitable volume cumulative particle size distribution graph can be formed, and during electrode rolling, smaller particles can effectively fill the gaps between larger particles, resulting in excellent electrode density, reduced particle cracking, and reduced side reactions between the positive electrode active material and electrolyte.

[0055] On the other hand, the positive electrode material powder may have an SP value of 0.20 or more and 0.33 or less, represented by the following formula (2).

[0056] Formula (2): SP=(D 50 -D min ) / (D max -D 50 )

[0057] The SP value represented by formula (2) is preferably 0.23 or more and 0.33 or less, more preferably 0.25 or more and 0.32 or less. When the SP value represented by formula (2) satisfies the above range, a suitable volume cumulative particle size distribution graph can be formed, resulting in less particle breakage and reduced side reactions with the electrolyte at high voltage.

[0058] On the other hand, when the positive electrode material powder is pressurized at 9 tons, the generation rate of fine particles with a particle size of 1 μm or less may be 3 volume% or less, preferably 2.8 volume% or less, more preferably 2.5 volume% or less, and even more preferably 2 volume% or less. Surface side reactions of the positive electrode active material are mainly caused by the generation of fine particles of the positive electrode active material. If a large amount of fine particles with a particle size of 1 μm or less are generated, the side reactions with the electrolyte become more severe, which can adversely affect the lifespan characteristics and continuous charging characteristics.

[0059] positive electrode Next, the positive electrode according to the present invention will be described. The positive electrode according to the present invention includes the positive electrode material powder of the present invention described above. Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer includes the positive electrode material powder of the present invention. Since the positive electrode material powder has been described above, a detailed explanation will be omitted, and only the remaining components will be described in detail below.

[0060] The positive electrode current collector may contain a highly conductive metal, and the positive electrode active material layer may adhere to it easily, but it is not particularly limited as long as it is unreactive within the battery voltage range. Examples of the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, heat-treated carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. The positive electrode current collector may also typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to enhance the adhesion of the positive electrode active material. For example, it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0061] The positive electrode active material layer may, as needed, selectively contain a conductive material and a binder along with the positive electrode material powder. In this case, the positive electrode material powder may be included in an amount of 80% to 99% by weight, more specifically 90% to 98% by weight, relative to the total weight of the positive electrode active material layer.

[0062] The conductive material is used to impart conductivity to the electrodes and can be used in any battery without particular limitations as long as it has electronic conductivity without causing a chemical change. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One of these may be used alone or in mixtures of two or more. The conductive material may be included in an amount of 0.01% to 10% by weight, preferably 0.1% to 9% by weight, and more preferably 0.1% to 5% by weight, relative to the total weight of the positive electrode active material layer.

[0063] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which the hydrogen atoms of these materials are substituted with Li, Na, or Ca, or various copolymers thereof. One of these materials alone or a mixture of two or more may be used. The binder may be present in an amount of 1% to 30% by weight, preferably 1% to 20% by weight, and more preferably 1% to 10% by weight, relative to the total weight of the positive electrode active material layer.

[0064] The positive electrode can be manufactured by a conventional method for manufacturing a positive electrode, except that the positive electrode material powder described above is used. Specifically, it can be manufactured by coating a positive electrode slurry composition, prepared by dissolving or dispersing the positive electrode material powder and, if necessary, a binder, conductive material, and dispersant in a solvent, onto a positive electrode current collector, followed by drying and rolling.

[0065] The solvent may be a solvent commonly used in the art, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these alone or a mixture of two or more may be used. The amount of solvent used should be sufficient to dissolve or disperse the cathode active material, conductive material, binder, and dispersant, taking into account the coating thickness of the slurry and the manufacturing yield, and to have a viscosity that allows for excellent thickness uniformity when applied for cathode manufacturing.

[0066] Alternatively, the positive electrode can also be manufactured by casting the positive electrode slurry composition onto another support, peeling it off the support, and then laminating the resulting film onto the positive electrode current collector.

[0067] Lithium-ion battery Next, the lithium secondary battery according to the present invention will be described. The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite the positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte. Since the positive electrode is the same as described above, a detailed explanation will be omitted, and only the remaining components will be described in detail below.

[0068] Furthermore, the lithium secondary battery may selectively further include a battery container for housing the electrode assembly comprising the positive electrode, negative electrode, and separator, and a sealing member for sealing the battery container.

[0069] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector. The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The negative electrode current collector may also have a thickness of 3 μm to 500 μm, and, similar to the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it may be used in various forms such as film, sheet, foil, mesh, porous material, foam, and nonwoven fabric.

[0070] The negative electrode active material layer selectively includes a binder and a conductive material together with the negative electrode active material. As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO2. βExamples include lithium-doped and dedoped metal oxides such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the metallic compound and carbonaceous material, such as Si-C composites or Sn-C composites. One or more of these mixtures may be used. A metallic lithium thin film may also be used as the negative electrode active material. As for the carbon material, either low-crystallinity carbon or high-crystallinity carbon may be used. Typical examples of low-crystalline carbon include soft carbon and hard carbon, while typical examples of high-crystalline carbon include amorphous, plate-like, flaky, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature heat-treated carbon such as petroleum or coal tar pitch-derived cokes.

[0071] The negative electrode active material may be included in an amount of 80% to 99% by weight, 82% to 99% by weight, or 84% to 99% by weight, based on the total weight of the negative electrode active material layer.

[0072] The binder is a component that helps to bond the conductive material, active material, and current collector, and is usually added at a concentration of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0073] The conductive material is a component for further improving the conductivity of the negative electrode active material and may be included in an amount of 1% to 30% by weight, 1% to 20% by weight, or 1% to 10% by weight relative to the total weight of the negative electrode active material layer. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery and is conductive, and may be used, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; carbon fluoride; metal powders such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0074] The negative electrode active material layer can be manufactured by coating a negative electrode slurry composition, which is prepared by dissolving or dispersing a negative electrode active material and a binder and conductive material selectively in a solvent, onto a negative electrode current collector and then drying it, or by casting the negative electrode slurry composition onto another support, peeling it off the support, and then laminating the resulting film onto the negative electrode current collector.

[0075] On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Generally, any separator commonly used in lithium secondary batteries can be used without particular limitations, and it is especially preferable that the separator has low resistance to ion movement of the electrolyte and excellent electrolyte moisture absorption capacity. Specifically, porous polymer films, such as porous polymer films made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof may be used. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used. Furthermore, to ensure heat resistance or mechanical strength, coated separators containing ceramic components or polymeric substances may be used, and they may be selectively used as single-layer or multi-layer structures.

[0076] Furthermore, the electrolytes used in the present invention include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0077] Specifically, the electrolyte may include an organic solvent and a lithium salt. The organic solvent can be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move, without any particular limitations. Specifically, the organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a hydrocarbon group with 2 to 20 carbon atoms in a linear, branched, or cyclic structure, and may include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used. Among these, carbonate solvents are preferred, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate) having high ionic conductivity and high dielectric constant that can improve the charge and discharge performance of the battery and a low-viscosity linear carbonate compound (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) is more preferred.

[0078] The lithium salt can be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the anion of the lithium salt is F - 、Cl - 、Br - 、I - 、NO3 - 、N(CN)2 - 、BF4 - 、CF3CF2SO3 - 、(CF3SO2)2N - 、(FSO2)2N - 、CF3CF2(CF3)2CO - 、(CF3SO2)2CH - 、(SF5)3C - 、(CF3SO2)3C - 、CF3(CF2)7SO3 - 、CF3CO2 - 、CH3CO2 - 、SCN - 、and at least one selected from the group consisting of (CF3CF2SO2)2N - may be used. Examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably used within the range of 0.1 M to 4.0 M, more preferably 0.5 M to 3.0 M, and even more preferably 1.0 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte has suitable conductivity and viscosity, so it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0079] In addition to the components of the electrolyte, the electrolyte may further contain one or more additives for purposes such as improving battery life characteristics, suppressing the decrease in battery capacity, and improving battery discharge capacity. These additives may include, for example, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. In this case, the additives may be present in an amount of 0.1 to 10.0% by weight relative to the total weight of the electrolyte.

[0080] As described above, the lithium secondary battery according to the present invention has excellent stability and electrochemical performance even at high voltages, so the charging termination voltage during operation may be 4.35V or higher, and when operated at such a high operating voltage, it can achieve superior high capacity characteristics compared to conventional lithium secondary batteries. The operating voltage of the lithium secondary battery according to the present invention may be 2.0V to 4.5V, preferably 2.0V to 4.0V.

[0081] Furthermore, the lithium secondary battery according to the present invention exhibits excellent discharge capacity, output characteristics, and capacity retention rate stably, making it useful in portable devices such as mobile phones, laptop computers, and digital cameras, as well as in the electric vehicle sector, including hybrid electric vehicles (HEVs).

[0082] Accordingly, according to another embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided. The battery module or battery pack can be used as a power source for one or more medium-to-large devices, including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0083] Hereinafter, embodiments of the present invention will be described in detail so that those with ordinary skill in the art to which the present invention pertains can easily implement it. However, the present invention may be realized in various different forms and is not limited to the embodiments described herein. The present invention will be described in more detail below with reference to specific examples.

[0084] Example 1 <Precursor manufacturing> After adding 4 L of distilled water to a coprecipitation reactor (capacity 20 L), and maintaining a temperature of 50°C under a nitrogen atmosphere, 100 mL of 28 wt% aqueous ammonia solution was added. Then, a 3.2 mol / L transition metal solution, prepared by mixing NiSO4, CoSO4, and MnSO4 in a nickel:cobalt:manganese molar ratio of 0.6:0.1:0.3, was continuously added to the reactor at a rate of 30 mL / hr and 42 mL / hr of 28 wt% aqueous ammonia solution. The mixture was stirred at an impeller speed of 400 rpm, and the coprecipitation reaction was carried out for 24 hours while adding a 40 wt% sodium hydroxide solution to maintain the pH of the reaction solution at 9.0, thereby forming precursor particles. The aforementioned precursor particles were separated and washed, and then dried in an oven at 130°C to produce a precursor.

[0085] <Manufacturing of positive electrode material powder> The cathode active material precursor, LiOH, manufactured as described above, was mixed with (Ni+Co+Mn):Li in a molar ratio of 1:1.05, and then calcined at 940°C for 20 hours to produce cathode material powder.

[0086] Subsequently, the cathode material powder was coarsely ground once using a jaw crusher at a rotational speed of 200 rpm, and then dry-ground once using a jet mill under conditions of a gas pressure of 10 bar and a gas velocity of 350 m / s to a level of 4 μm. The composition of the cathode material powder produced above is Li[Ni 0.6 Co 0.1 Mn 0.3 It was 100.

[0087] Subsequently, the cathode material powder, Al2O3, and WO3 were mixed so that the molar ratio of the cathode material powder:Al:W was 100:0.3:0.1, and then fired at 450°C for 5 hours to produce cathode material powder with Al and W coating layers formed on it.

[0088] Example 2 The cathode material powder was produced in the same manner as in Example 1, except that after mixing the cathode material powder, Al2O3, and WO3, a coating layer was formed by firing at 550°C for 5 hours.

[0089] Example 3 A cathode material powder was produced in the same manner as in Example 1, except that the cathode active material precursor and LiOH were mixed and then calcined at 930°C for 20 hours.

[0090] Comparative Example 1 The cathode material powder was manufactured in the same manner as in Example 1, except that it was first coarsely ground once using a jaw crusher at a rotational speed of 200 rpm, and then ground three times using a pin mill at a rotational speed of 10,000 rpm.

[0091] Comparative Example 2 The cathode material powder was produced in the same manner as in Example 1, except that the cathode material powder was produced by mixing the cathode active material precursor with LiOH and then firing it at 930°C for 20 hours, followed by coarse grinding once using a jaw crusher at a rotational speed of 200 rpm, and then grinding three times using a pin mill at a rotational speed of 10,000 rpm.

[0092] Comparative Example 3 The cathode material powder was manufactured in the same manner as in Example 1, except that it was first coarsely ground once using a jaw crusher at a rotational speed of 200 rpm, and then ground four times using a pin mill at a rotational speed of 10,000 rpm.

[0093] Comparative Example 4 The cathode material powder was produced in the same manner as in Example 1, except that the cathode material powder was produced by mixing the cathode active material precursor with LiOH and then firing it at 930°C for 20 hours, followed by coarse grinding once using a jaw crusher at a rotational speed of 200 rpm, and then grinding four times using a pin mill at a rotational speed of 10,000 rpm.

[0094] Experimental Example 1: Measurement of Volume Cumulative Particle Size Distribution and BET Specific Surface Area The volume cumulative particle size distribution (PSD) of the cathode material powders produced in Examples 1-3 and Comparative Examples 1-4 was measured, and P0 and D were determined based on the volume cumulative particle size distribution. min , D 50 , D max This is shown in [Table 1] below.

[0095] Furthermore, 3g of the cathode material powder produced in Examples 1-3 and Comparative Examples 1-4 was taken and measured using the BET method with BELSORP-mini II, and the measurement results are shown in Table 1 below. Furthermore, the PCF values ​​obtained using the method described above are shown in [Table 1] below.

[0096] [Table 1]

[0097] Experimental Example 2: Measurement of Particle Splitting Five g of the cathode material powder produced in Examples 1-3 and Comparative Examples 1-4 was placed in a cylindrical metal mold with a diameter of 1.2 cm and pressed under a pressure of 9 tons. The volumetric cumulative particle size distribution (PSD) was then measured to determine the rate of fine particle generation with a particle size of 1 μm or less. The particle size distribution was measured using a Microtrac S-3500, and the rate of fine particle generation with a particle size of 1 μm or less was converted to a volume percentage relative to the total weight of the cathode material powder. The graphs of the volumetric cumulative particle size distribution before and after 9-ton pressure pressing for Example 1 and Comparative Example 2 are shown in Figures 1 and 2, respectively, and the rate of fine particle generation with a particle size of 1 μm or less for Examples 1-3 and Comparative Examples 1-4 is shown in Table 2.

[0098] [Table 2]

[0099] From [Table 2] above, it can be confirmed that in the case of the cathode material powders of Examples 1 to 3 whose PCF values ​​meet the range of the present invention, the amount of fine powder generated when pressed at a pressure of 9 tons is significantly less compared to the cathode material powders manufactured by Comparative Examples 1 to 4.

[0100] Experimental Example 3: Evaluation of Continuous Charging Characteristics The cathode material powders, conductive material (carbon black), and binder (PVDF) from Examples 1-3 and Comparative Examples 1-4, prepared as described above, were mixed in N-methylpyrrolidone in a weight ratio of 95:2:3 to produce cathode slurries containing the cathode material powders from Examples 1-3 and Comparative Examples 1-4. The cathode slurry was applied to one side of an aluminum current collector, dried at 60°C, and then rolled to produce a cathode. Lithium metal was used as the negative electrode.

[0101] An electrode assembly was manufactured by interposing a porous polyethylene separator between the positive electrode and the negative electrode. After positioning the electrode assembly inside a battery case, an electrolyte was injected into the case to produce a half-cell. The electrolyte was prepared by dissolving 1.0 M LiPF6 in a mixed organic solvent consisting of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 3:4:3.

[0102] Each of the half-cell batteries manufactured as described above was charged to a high voltage of 4.8V with a constant current of 0.1C at 60°C, and the current after the application of the constant voltage was measured. The measurement results are shown in Figure 3. Furthermore, in the graph of Figure 3, only the current is shown in Figure 4, and only the voltage is shown in Figure 5.

[0103] In the case of half-cell batteries using the positive electrode material powders of Examples 1 to 3, particle cracking is reduced and side reactions between the positive electrode active material and the electrolyte are reduced compared to half-cell batteries using the positive electrode material powders of the comparative examples. As a result, the leakage current during continuous charging is reduced, and the continuous charging results are superior, as can be seen from Figures 3 and 4.

Claims

1. A cathode material powder containing a cathode active material which includes lithium nickel-based oxide particles having a Ni content of 50 mol% to 80 mol% among all metals excluding lithium, The lithium nickel oxide particles are in the form of single particles consisting of one single nodule or pseudo-single particles which are composites of 30 or fewer nodules. The PCF value represented by the following formula (1) satisfies 2.0 or more and 3.4 or less, Formula (1): particle cracking factor(PCF)=S ＢＥＴ ×P ０ ×(D ５０ -D ｍｉｎ ) / (D ｍａｘ -D ５０ ) In formula (1) above, S ＢＥＴ This is the BET specific surface area (unit: m²) of the positive electrode material powder. ２ / g) and The aforementioned P ０ is the intensity (unit: vol%) of the maximum peak in the volume cumulative particle size distribution measured for the aforementioned positive electrode material powder using the laser diffraction method, The aforementioned D ５０ This is the particle size when the volume cumulative amount in the volume cumulative particle size distribution of the positive electrode material powder is 50%. The aforementioned D ｍｉｎ This is the minimum particle size in the volume cumulative particle size distribution of the positive electrode material powder, The aforementioned D ｍａｘ The cathode material powder is the cathode material powder having the largest particle size in the volume cumulative particle size distribution of the cathode material powder.

2. The lithium nickel oxide particles are represented by the following [Chemical Formula 1], [Chemical formula 1] Li ａ Ni ｂ Co ｃ Mn ｄ M １ ｅ O ２ In the above chemical formula 1, M １ The positive electrode material powder according to claim 1, wherein is one or more selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and satisfies 0.8 ≤ a ≤ 1.2, 0.5 ≤ b ≤ 0.8, 0 < c ≤ 0.3, 0 < d ≤ 0.4, and 0 ≤ e ≤ 0.

2.

3. The BET specific surface area of ​​the aforementioned cathode material powder is 0.2 m². ２ / g or more 1.3m ２ The positive electrode material powder according to claim 1, wherein the amount is less than or equal to / g.

4. The aforementioned P ０ The positive electrode material powder according to claim 1, wherein the ratio is 8 or higher.

5. The aforementioned D ５０ The positive electrode material powder according to claim 1, wherein the particle size is 1 μm or more and 10 μm or less.

6. The aforementioned D ｍｉｎ The positive electrode material powder according to claim 1, wherein the particle size is 0.75 μm or more and 2.0 μm or less.

7. The aforementioned D ｍａｘ The cathode material powder according to claim 1, wherein the particle size is 8 μm or more and 18 μm or less.

8. The SP value represented by the following formula (2) is 0.20 or more and 0.33 or less, Formula (2): SP=(D ５０ -D ｍｉｎ ) / (D ｍａｘ -D ５０ ) The positive electrode material powder according to claim 1.

9. The positive electrode material powder according to claim 1, wherein the PCF value is 2.5 or more and 3.2 or less.

10. The cathode material powder according to claim 1, wherein when the cathode material powder is pressurized at 9 tons, the generation rate of fine particles with a particle size of 1 μm or less is 3 volume% or less.

11. A positive electrode comprising the positive electrode material powder described in claim 1.

12. The positive electrode according to claim 11, The negative electrode and, A separator interposed between the positive electrode and the negative electrode, A lithium secondary battery containing an electrolyte.

13. The lithium secondary battery according to claim 12, wherein the charging termination voltage when the lithium secondary battery is in operation is 4.35V or higher.

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