Positive electrode active material precursor for lithium secondary battery, method for preparing same, positive electrode active material for lithium secondary battery, and lithium secondary battery

Abstract

A positive electrode active material precursor for a lithium secondary battery according to an embodiment of the present invention may comprise: a first positive electrode active material precursor particle comprising a core part and a shell part, the core part and the shell part comprising a transition metal containing nickel; and a second positive electrode active material precursor particle containing a transition metal containing nickel. In the transition metal of the second positive electrode active material precursor particles, the molar fraction of nickel can be kept constant throughout the second positive electrode active material precursor particles. The average particle diameter (D50) of the core parts of the first positive electrode active material precursor particles may be larger than the average particle diameter (D50) of the second positive electrode active material precursor particles.

Description

Technical Field

[0001] This invention relates to a precursor of a positive electrode active material for lithium secondary batteries, a positive electrode active material for lithium secondary batteries, and a lithium secondary battery comprising the positive electrode active material. More specifically, it relates to a nickel-containing precursor of a positive electrode active material for lithium secondary batteries, a positive electrode active material for lithium secondary batteries, and a lithium secondary battery comprising the positive electrode active material. Background Technology

[0002] Rechargeable batteries are batteries that can be repeatedly charged and discharged. With the development of the information communication and display industries, rechargeable batteries are widely used as power sources for portable electronic communication devices such as portable cameras, mobile phones, and laptops (PCs). In addition, in recent years, battery packs that include rechargeable batteries have been developed for use as power sources for environmentally friendly vehicles such as electric vehicles.

[0003] Secondary batteries can be categorized into, for example, lithium secondary batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium secondary batteries have high operating voltage and energy density per unit weight, and are advantageous for charging speed and lightweight design, so they are being actively developed.

[0004] To improve the capacity characteristics of lithium-ion batteries, high-nickel (High-Ni) based lithium oxides with increased nickel content can be used as the positive electrode active material in the lithium-ion battery. The positive electrode active material can be prepared by reacting a precursor containing a transition metal with a lithium source.

[0005] However, the aforementioned high-nickel-based lithium oxides may be structurally unstable. Therefore, there is a need to develop a transition metal-containing precursor that can improve both the capacity characteristics and structural stability of secondary batteries. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] One technical problem of the present invention is to provide a positive electrode active material precursor for lithium secondary batteries that can improve the lifespan characteristics and initial efficiency of lithium secondary batteries.

[0008] One technical problem of the present invention is to provide a method for preparing the positive electrode active material precursor for lithium secondary batteries.

[0009] One technical problem of the present invention is to provide a positive electrode active material for lithium secondary batteries formed from the positive electrode active material precursor.

[0010] One technical problem of the present invention is to provide a lithium secondary battery comprising the positive electrode active material for a lithium secondary battery.

[0011] (II) Technical Solution

[0012] According to an exemplary embodiment of the present invention, a positive electrode active material precursor for a lithium secondary battery comprises: a first positive electrode active material precursor particle, the first positive electrode active material precursor particle comprising a core and a shell, the core and shell comprising a nickel-containing transition metal; and a second positive electrode active material precursor particle, the second positive electrode active material precursor particle comprising a nickel-containing transition metal. In the transition metal of the second positive electrode active material precursor particle, the molar fraction of nickel remains constant throughout the second positive electrode active material precursor particle. The average particle size (D) of the core of the first positive electrode active material precursor particle is... 50 The particle size of the precursor particles of the second positive electrode active material is greater than the average particle size (D). 50 ).

[0013] In some embodiments, the average particle size (D) of the core is... 50 The diameter can range from 8μm to 13μm.

[0014] In some embodiments, the average particle size (D) of the second positive electrode active material precursor particles 50 The diameter can range from 3μm to 6μm.

[0015] In some embodiments, the average molar fraction of nickel in the transition metal of the first positive electrode active material precursor particles may be greater than the average molar fraction of nickel in the transition metal of the second positive electrode active material precursor particles.

[0016] In some implementations, the transition metal may further comprise cobalt and manganese.

[0017] According to an exemplary embodiment, the positive electrode active material for a lithium secondary battery comprises lithium transition metal oxide particles formed from the aforementioned positive electrode active material precursor for a lithium secondary battery.

[0018] A lithium secondary battery according to an exemplary embodiment includes: a positive electrode comprising the above-described positive electrode active material for a lithium secondary battery; a negative electrode; and a separator disposed between the positive electrode and the negative electrode.

[0019] According to an exemplary embodiment of the method for preparing a positive electrode active material precursor for lithium secondary batteries, a nickel-containing first transition metal source is added to a first reactor to prepare a primary precursor. The primary precursor and a nickel-containing second transition metal source are added to a second reactor to prepare a first positive electrode active material precursor having a core-shell structure. In one or more of the first and second reactors, a second positive electrode active material precursor with a uniform nickel content throughout the particles is prepared. The first and second reactors are either continuous stirred tank reactors (CSTRs) or batch reactors, and are distinct from each other.

[0020] In some embodiments, the first reactor is the batch reactor, the second reactor is the CSTR, and the preparation of the second positive electrode active material precursor can be carried out simultaneously with the preparation of the first positive electrode active material precursor in the second reactor.

[0021] In some implementations, the preparation of the second positive electrode active material precursor can be carried out simultaneously with the formation of the shell portion of the first positive electrode active material precursor.

[0022] In some embodiments, the first reactor is the CSTR, and the second reactor is the batch reactor. When preparing the primary precursor, the average particle size (D) can be prepared in the first reactor. 50 The second primary precursor and the second primary precursor are different from each other. The second primary precursor and the second transition metal source can be added to the second reactor to prepare the second positive electrode active material precursor.

[0023] In some embodiments, the first primary precursor and the second primary precursor prepared in the first reactor can be added together to the second reactor, and a shell is formed only on the first primary precursor added to the second reactor, thereby preparing the first positive electrode active material precursor.

[0024] In some embodiments, the first reactor is a CSTR, and the nickel content in the total weight of the first transition metal source can be greater than the nickel content in the total weight of the second transition metal source.

[0025] In some embodiments, the first reactor is a batch reactor, and the nickel content in the total weight of the first transition metal source may be less than the nickel content in the total weight of the second transition metal source.

[0026] In some implementations, the primary precursor may be added to an intermediate reactor before being added to the second reactor.

[0027] (III) Beneficial Effects

[0028] According to an exemplary embodiment of the present invention, the particle size of the positive electrode active material precursor for lithium secondary batteries can have a bimodal distribution. A lithium secondary battery precursor with a wide surface area can improve charge / discharge efficiency, while a lithium secondary battery precursor with a narrow surface area can provide secondary batteries with improved lifespan characteristics.

[0029] Furthermore, side reactions between the positive electrode active material for lithium secondary batteries formed from the positive electrode active material precursor of the exemplary embodiment of the present invention and the electrolyte can be reduced. Therefore, the lifespan characteristics and charge / discharge efficiency of the lithium secondary battery can be improved.

[0030] The lithium secondary battery of this invention can be widely used in green technology fields such as electric vehicles, battery charging stations, and other battery-based solar and wind power generation. The positive electrode active material precursor, its preparation method, and the lithium secondary battery containing the positive electrode active material precursor of this invention can be used in eco-friendly electric vehicles and hybrid vehicles that prevent climate change by suppressing air pollution and greenhouse gas emissions. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of an apparatus for preparing a positive electrode active material precursor according to an exemplary embodiment.

[0032] Figure 2 and Figure 3 This is a process flow diagram illustrating a method for preparing a positive electrode active material precursor according to an exemplary embodiment.

[0033] Figure 4 and Figure 5 These are schematic plan views and schematic cross-sectional views of a lithium secondary battery according to an exemplary embodiment. Detailed Implementation

[0034] The present invention provides a positive electrode active material precursor for a lithium secondary battery (hereinafter referred to as "positive electrode active material precursor"), a positive electrode active material for a lithium secondary battery formed from the positive electrode active material precursor (hereinafter referred to as "positive electrode active material"), and a lithium secondary battery containing the positive electrode active material (hereinafter referred to as "secondary battery").

[0035] The present invention will now be described in detail with reference to the accompanying drawings. However, these are merely exemplary embodiments, and the present invention is not limited to the specific embodiments described herein.

[0036] According to an exemplary embodiment, the positive electrode active material precursor may comprise a first positive electrode active material precursor particle and a second positive electrode active material precursor particle. The first positive electrode active material precursor particle may comprise a core-shell structured compound. The second positive electrode active material precursor particle may comprise a non-core-shell structured compound. The first positive electrode active material precursor particle can improve the charge / discharge characteristics of the secondary battery, while the second positive electrode active material precursor particle can improve the lifespan characteristics of the secondary battery.

[0037] According to an exemplary embodiment, the first positive electrode active material precursor particle may include a core containing a nickel-containing transition metal and a shell containing a nickel-containing transition metal.

[0038] According to an exemplary embodiment, the second positive electrode active material precursor particles may contain a nickel-containing transition metal.

[0039] According to an exemplary embodiment, the average particle size (D) of the core portion of the first positive electrode active material precursor particle is... 50 The particle size can be larger than the average particle size (D) of the second positive electrode active material precursor particles. 50 ).

[0040] When the average particle size (D) of the core of the first positive electrode active material precursor particles 50 If the amount is reduced excessively, the shell may not be able to be deposited on the core.

[0041] When the average particle size of the second positive electrode active material precursor particles (D) 50 When the amount of metal is excessive, an additional transition metal layer may form on the surface of the second positive electrode active material precursor particles, thereby detaching it from the non-core-shell structure.

[0042] By adjusting the average particle size (D) of the core portion of the first positive electrode active material precursor particles... 50 The particle size is maintained at a value greater than the average particle size (D) of the second positive electrode active material precursor particles.50 This allows the first positive electrode active material precursor particles to form a core-shell structure, and the second positive electrode active material precursor particles to form a non-core-shell structure.

[0043] The term "average particle size (D)" used in this invention 50 "" refers to the particle size based on 50% of the volumetric cumulative particle size distribution. For example, the average particle size (D) 50 This can refer to measuring the particle size distribution using a particle size analyzer employing laser diffraction, where the particle size corresponds to the particle size of the 50% volume fraction accumulated from the smallest particle in the measured particle size distribution. In some embodiments, the average particle size (D) of the core portion of the first positive electrode active material precursor particles... 50 The core can be 8 μm to 13 μm, 9 μm to 13 μm, 9 μm to 12 μm, or 9.5 μm to 11 μm. Within these ranges, the transition metal can be stably deposited on the core. Therefore, the first positive electrode active material precursor particles can be formed into a core-shell structure, which can improve the charge / discharge characteristics of the secondary battery.

[0044] In some embodiments, the average particle size (D) of the first positive electrode active material precursor particles is... 50 The particle size can be 10 μm to 18 μm, 12 μm to 18 μm, 14 μm to 18 μm, or 14 μm to 16 μm. Within these ranges, the average specific surface area of ​​the first positive electrode active material precursor particles can be sufficiently increased. Therefore, the reaction area of ​​the positive electrode active material formed from the first positive electrode active material precursor particles can be increased, thereby improving the charge / discharge characteristics of the secondary battery.

[0045] In some embodiments, the average particle size (D) of the second positive electrode active material precursor particles 50 The particle size can be 3μm to 6μm, 4μm to 6μm, or 4μm to 5μm. Within these ranges, no additional transition metal layer may be formed on the second positive electrode active material precursor particles. Therefore, the second positive electrode active material precursor particles can maintain a non-core-shell structure, and the size of the positive electrode active material formed from the second positive electrode active material precursor particles can be small. Therefore, the lifespan characteristics of the secondary battery containing the positive electrode active material can be improved.

[0046] In some embodiments, the transition metal may further comprise cobalt and manganese. For example, the transition metal contained in the first positive electrode active material precursor particles may further comprise cobalt and manganese. For example, the transition metal contained in the second positive electrode active material precursor particles may further comprise cobalt and manganese.

[0047] In some embodiments, the first positive electrode active material precursor particles and the second positive electrode active material precursor particles may comprise a transition metal hydroxide represented by the following chemical formula 1.

[0048] [Chemical Formula 1]

[0049] Ni a1 M b1 (OH) 2+c1

[0050] In chemical formula 1, the values ​​can be 0.6 ≤ a1 ≤ 0.99, 0.01 ≤ b1 ≤ 0.4, and -0.5 ≤ c1 ≤ 0.1. As mentioned above, M can contain Co and / or Mn.

[0051] The chemical structure represented by Formula 1 indicates the bonding relationships contained in the layered or crystalline structure of the cathode active material precursor, and does not exclude other additional elements. For example, M may contain Co and / or Mn, and Co and / or Mn may be provided together with Ni as the main active element of the cathode active material precursor. Formula 1 is provided to represent the bonding relationships of the main active element, and it should be understood that Formula 1 includes the introduction and substitution of additional elements.

[0052] In one embodiment, in addition to the primary active element, auxiliary elements may be further included to enhance the chemical stability of the positive electrode active material precursor or the layered / crystal structure. These auxiliary elements may be incorporated into the layered / crystal structure to form a bond, and this should be understood to also include the chemical structures represented by Formula 1.

[0053] The auxiliary element may include at least one of, for example, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may function as an auxiliary active element, together with Co or Mn, to contribute to the capacity / power activity of the positive electrode active material formed from the positive electrode active material precursor; for example, Al.

[0054] In one embodiment, the auxiliary element may include at least one selected from Al, Ti, W, Sr, Zr, Ta, Nb, Mo, and B. Therefore, the capacity / power characteristics of the positive electrode active material formed from the positive electrode active material precursor can be further improved.

[0055] For example, the positive electrode active material precursor or the transition metal hydroxide can be represented by the following chemical formula 1-1.

[0056] [Chemical Formula 1-1]

[0057] Ni a1 M1 b11 M2 b12 (OH) 2+c1

[0058] In chemical formula 1-1, M1 may contain Co and / or Mn. M2 may contain the aforementioned auxiliary elements. In chemical formula 1-1, the following conditions may be met: 0.6≤a1≤0.99, 0.01≤b11+b12≤0.4, -0.5≤c1≤0.1.

[0059] The positive electrode active material precursor may comprise a nickel-cobalt-manganese (NCM)-based hydroxide. In this case, an NCM-based hydroxide with increased nickel content can be used.

[0060] Ni can be provided as a transition metal related to the power and capacity of lithium secondary batteries. Therefore, as described above, by forming the positive electrode active material and the secondary battery from a positive electrode active material precursor with a high content (High-Ni), a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0061] However, increasing the Ni content may relatively reduce the long-term storage stability and lifetime stability of the cathode or secondary battery, and may increase side reactions with the electrolyte. However, according to an exemplary embodiment, conductivity can be maintained by including Co, while lifetime stability and capacity retention characteristics can be improved by including Mn.

[0062] In the NCM-based hydroxide, the Ni content (e.g., the mole fraction of nickel in the total moles of nickel, cobalt, and manganese) can be 0.6 or more, 0.7 or more, or 0.8 or more.

[0063] In some embodiments, the average molar fraction of nickel in the transition metal of the first positive electrode active material precursor particles can be greater than the average molar fraction of nickel in the transition metal of the second positive electrode active material precursor particles. Therefore, the positive electrode active material formed from the first positive electrode active material precursor particles can improve charge / discharge characteristics, while the positive electrode active material formed from the second positive electrode active material precursor particles can simultaneously improve lifetime characteristics.

[0064] In one embodiment, the Ni content in the first positive electrode active material precursor particles can be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95. Therefore, the charge / discharge capacity and efficiency of the secondary battery comprising the positive electrode active material formed from the first positive electrode active material precursor particles can be improved.

[0065] In one embodiment, the Ni content in the second positive electrode active material precursor particles can be 0.8 to 0.95, 0.80 to 0.93, 0.80 to 0.90, or 0.80 to 0.89. Therefore, the lifespan characteristics of a secondary battery containing a positive electrode active material formed from the second positive electrode active material precursor particles can be improved.

[0066] In some embodiments, the average molar fraction of nickel in the transition metal of the first positive electrode active material precursor particles may also be less than the average molar fraction of nickel in the transition metal of the second positive electrode active material precursor particles. For example, the average molar fraction of nickel in the transition metal of the positive electrode active material precursor particles can be adjusted according to the following method for preparing the positive electrode active material precursor.

[0067] In one embodiment, the Ni content of the second positive electrode active material precursor particles can be 0.8 to 0.98, 0.85 to 0.97, 0.90 to 0.96, or 0.92 to 0.95. Therefore, by simultaneously including the second positive electrode active material precursor particles with high nickel content and the first positive electrode active material precursor particles, the capacity characteristics of the secondary battery can be further improved.

[0068] Figure 1 This is a schematic diagram of an apparatus for preparing a positive electrode active material precursor according to an exemplary embodiment.

[0069] Figure 2 and Figure 3 This is a process flow diagram illustrating a method for preparing a positive electrode active material precursor according to an exemplary embodiment.

[0070] The following will refer to Figures 1 to 3 A method for preparing a positive electrode active material precursor according to an exemplary embodiment will be described.

[0071] In an exemplary embodiment, a first transition metal source containing a nickel source may be added to a first reactor 20 to prepare a primary precursor. The primary precursor may be a nickel-containing transition metal hydroxide.

[0072] In some embodiments, the first transition metal source may comprise nickel. The nickel source may include, for example, nickel sulfate (NiSO4), nickel hydroxide (Ni(OH)2), nickel nitrate (Ni(NO3)2), nickel acetate (Ni(CH3CO2)2), or their hydrated forms, and may be included in the first transition metal source in the aforementioned forms.

[0073] In some embodiments, the first transition metal source may further comprise at least one of cobalt and manganese. For example, the first transition metal source may comprise nickel while also comprising cobalt and manganese.

[0074] The cobalt source may include, for example, cobalt sulfate (CoSO4), cobalt hydroxide (Co(OH)2), cobalt nitrate (Co(NO3)2), cobalt carbonate (CoCO3), or their hydrated forms, and may be included in the first transition metal source in the aforementioned forms.

[0075] The manganese source may include, for example, manganese sulfate (MnSO4), manganese hydroxide (Mn(OH)2), manganese nitrate (Mn(NO3)2), manganese acetate (Mn(CH3CO2)2) or their hydrated forms, and may be included in the first transition metal source in the above-described forms.

[0076] In one embodiment, the nickel, cobalt, and manganese may be contained in the first transition metal source in the forms of nickel sulfate, cobalt sulfate, and manganese sulfate, respectively. Therefore, the pH of the first transition metal source containing the nickel, cobalt, and manganese can be appropriately adjusted to increase the rate of the co-precipitation reaction.

[0077] In some embodiments, the first transition metal source may further include additional metal sources. For example, the first transition metal source may further include one or more metal sources selected from aluminum sulfate (Al2(SO4)3), titanium sulfate (Ti(SO4)2), tungsten hexafluoride (WF6), strontium chloride (SrCl2), zirconium sulfate (Zr(SO4)2), tantalum chloride (TaCl5), niobium sulfate (Nb2(SO4)5), molybdenum sulfate (Mo(SO4)3), and boron chloride (BCl3). Therefore, the charge / discharge characteristics of the positive electrode active material formed from the positive electrode active material precursor can be further improved.

[0078] In some embodiments, the aforementioned nickel-containing first transition metal source can be formed in the first transition metal addition container 10 and then added to the first reactor 20. For example, the first transition metal source can be formed by mixing a nickel source, a cobalt source, and a manganese source in the first transition metal addition container 10. For example, the first transition metal source can be continuously or discontinuously supplied to the first reactor 20 through the first addition flow path 15.

[0079] In one embodiment, a first transition metal source in an aqueous solution state formed by adding a solvent to a first transition metal addition container 10 can be supplied to a first reactor 20 via a first addition flow path 15. For example, the solvent may contain water.

[0080] An inert gas, chelating agent, and pH adjuster can be continuously added to the first reactor 20 along with the first transition metal source. Therefore, the nucleation and growth of the primary precursor can occur simultaneously. Thus, the primary precursor can be prepared in the first reactor 20.

[0081] The inert gas may include, for example, N2, Ar, H2, Ne, Xe, Kr, etc.

[0082] The chelating agent may include, for example, ammonia (e.g., NH4OH), ammonium bicarbonate (e.g., NH4HCO3), etc.

[0083] The pH adjuster may include, for example, ammonia, NaOH, etc.

[0084] In some embodiments, the weight ratio of the chelating agent (e.g., ammonia) to the first transition metal source can be 1 to 4, 1 to 3, or 2 to 3. Within these ranges, primary precursors can be stably prepared.

[0085] For example, in the first reactor 20, the primary precursor can be grown to have an average particle size (D) of 8 μm to 13 μm, 9 μm to 13 μm, 9 μm to 12 μm, or 9.5 μm to 11 μm. 50 Within the aforementioned range, further transition metals can be stably deposited on the primary precursor, thus the first positive electrode active material precursor can be formed as a core-shell structure.

[0086] According to an exemplary implementation, the primary precursor and a second transition metal source containing a nickel source are added to a second reactor 30 to prepare the first positive electrode active material precursor.

[0087] For example, the second transition metal source can be formed from the aforementioned nickel source, cobalt source, and manganese source, and can have the same or different composition as the first transition metal source.

[0088] For example, the primary precursor formed in the first reactor 20 can serve as the core of the first positive electrode active material precursor. Similarly, the transition metal layer further formed in the second reactor 30 can serve as the shell of the first positive electrode active material precursor. Therefore, the first positive electrode active material precursor can have a core-shell structure.

[0089] In some embodiments, the primary precursor prepared in the first reactor 20 may be added to the second reactor 30. For example, the primary precursor may be supplied to the second reactor 30 continuously. For example, the primary precursor may be supplied to the second reactor 30 discontinuously.

[0090] In some embodiments, a nickel-containing second transition metal source can be formed in the second transition metal addition container 40 and added to the second reactor 30. For example, the second transition metal source can be continuously supplied to the second reactor 30 through the second addition flow path 35. For example, the second transition metal source can be discontinuously supplied to the second reactor 30 through the second addition flow path 35.

[0091] In one embodiment, a second transition metal source, formed into a solution by adding a solvent to a second transition metal addition container 40, can be supplied to a second reactor 30 via a second addition flow path 35. For example, the solvent may contain water.

[0092] An inert gas, a chelating agent, and a pH adjuster are continuously added to the second reactor 30 along with the second transition metal source. Therefore, the primary precursor can be grown through a co-precipitation reaction. Thus, a first positive electrode active material precursor can be prepared in the second reactor 30.

[0093] The inert gas, chelating agent, and pH adjuster may be substantially the same as those added to the first reactor 20.

[0094] For example, the weight ratio of the chelating agent (e.g., ammonia) to the second transition metal source can be 1 to 4, 1 to 3, or 2 to 3. Within the above range, a first positive electrode active material precursor can be stably prepared.

[0095] In some embodiments, the first positive electrode active material precursor can be grown to have an average particle size (D) of 10 μm to 18 μm, 12 μm to 18 μm, 14 μm to 18 μm, or 14 μm to 16 μm. 50 Within the aforementioned range, the average specific surface area of ​​the first positive electrode active material precursor can be sufficiently increased. Therefore, the reaction area of ​​the positive electrode active material formed from the first positive electrode active material precursor can be increased, thereby improving the charge / discharge characteristics of the secondary battery.

[0096] According to an exemplary embodiment, a second positive electrode active material precursor having a uniform nickel content throughout the particles can be prepared in a first reactor 20 or a second reactor 30.

[0097] The term "uniform nickel content throughout the particle" as used in this invention can refer to particles that are substantially non-core-shell structured. For example, it can refer to particles where the nickel composition is uniform when measured at any two points on the particle. For example, it can refer to particles where the difference in the mole fraction of nickel measured at any two points on the particle (e.g., any two points on the particle surface or any two points inside the particle) is less than 0.05.

[0098] For example, while the primary precursor is being formed in the first reactor 20, the nucleus of the second positive electrode active material precursor can also be formed.

[0099] For example, while the first positive electrode active material precursor is formed from the primary precursor in the second reactor 30, the nucleus of the second positive electrode active material precursor can be grown.

[0100] In some embodiments, the second positive electrode active material precursor can be grown to have an average particle size (D) of 3 μm to 6 μm, 4 μm to 6 μm, or 4 μm to 5 μm. 50 Within the aforementioned range, no additional transition metal layer may be formed on the second positive electrode active material precursor. Therefore, the second positive electrode active material precursor can maintain a non-core-shell structure.

[0101] According to an exemplary embodiment, the first reactor 20 and the second reactor 30 may be either a continuous stirred tank reactor (CSTR) or a batch reactor, and the first reactor 20 and the second reactor 30 may be different reactors from each other.

[0102] For example, when the first reactor 20 is a CSTR, the second reactor 30 can be a batch reactor.

[0103] When using a batch reactor alone, the particle size distribution of the positive electrode active material precursor may become narrower. Therefore, the positive electrode active material precursor can have a unimodal particle size distribution. When a positive electrode active material is formed using a positive electrode active material precursor with a unimodal particle size distribution, the electrode density of the positive electrode may decrease.

[0104] When CSTR is used alone, the first positive electrode active material precursor may not have a core-shell morphology. When a non-core-shell morphology first positive electrode active material precursor is used to form the positive electrode active material, the charge / discharge capacity may decrease, and the structural stability of the positive electrode active material may decrease.

[0105] However, by using both CSTR and a batch reactor, it is possible to prepare a positive electrode active material precursor with a bimodal morphology while simultaneously preparing a positive electrode active material precursor with a stable core-shell structure. Therefore, the charge / discharge characteristics and lifetime characteristics of a secondary battery containing a positive electrode active material formed from the aforementioned positive electrode active material precursor can be improved simultaneously.

[0106] Depending on the type of the first reactor 20 and the second reactor 30, the specific order of the reaction may vary.

[0107] For example, when the first reactor 20 is a CSTR and the second reactor 30 is a batch reactor, primary precursors with different particle sizes (e.g., a first primary precursor and a second primary precursor) are formed in the first reactor 20, and the first positive electrode active material precursor and the second positive electrode active material precursor can be prepared from the primary precursors in the second reactor 30, respectively.

[0108] For example, when the first reactor 20 is a batch reactor and the second reactor 30 is a CSTR, a primary precursor is formed in the first reactor 20, a first positive electrode active material precursor is prepared from the primary precursor in the second reactor 30, and a second positive electrode active material precursor can be prepared separately.

[0109] In some implementations, the average particle size (D) of the primary precursor 50 The particle size can be larger than the average particle size (D) of the precursor of the second positive electrode active material. 50 Therefore, the primary precursor can be selectively grown. For example, the first positive electrode active material precursor can be formed as a core-shell structure, and the second positive electrode active material precursor can be formed as a non-core-shell structure. Thus, the lifetime and power characteristics of the positive electrode active material prepared from the first and second positive electrode active material precursors can be improved simultaneously.

[0110] Figure 2 This is a schematic process flow diagram illustrating a method for preparing a positive electrode active material precursor according to an exemplary embodiment.

[0111] Reference Figure 2 The first reactor 20 can be a batch reactor, and the second reactor 30 can be a CSTR.

[0112] In some embodiments, when the first reactor 20 is a batch reactor, a primary precursor can be prepared in the first reactor 20 (e.g., process S10). For example, the primary precursor can be the core of a first positive electrode active material precursor. For example, a co-precipitation reaction of a first transition metal source can be carried out. Thus, the core of the primary precursor can be formed and allowed to grow.

[0113] The coprecipitation reaction can be carried out at 50°C to 70°C, 55°C to 70°C, or 55°C to 65°C for 10 to 30 hours, 15 to 30 hours, or 15 to 25 hours, respectively. Furthermore, the coprecipitation reaction can be carried out with stirring at pH 10 to 13, 10 to 12, or 11 to 12 at 500 rpm to 1500 rpm, 700 rpm to 1500 rpm, or 700 rpm to 1200 rpm. Within the above ranges, a primary precursor of the above size can be prepared.

[0114] In some embodiments, when the first reactor 20 is a batch reactor, the primary precursor prepared in the first reactor 20 can be added to the intermediate reactor 25 (e.g., process S20). For example, the primary precursor prepared in the first reactor 20 can be added to the intermediate reactor 25 through the first transfer path 23.

[0115] In some embodiments, the intermediate reactor 25 can be a batch reactor. Therefore, the primary active material, etc., added to the intermediate reactor 25 can be stirred. Furthermore, no additional transition metal source may be added to the intermediate reactor 25. Therefore, no further co-precipitation reaction occurs in the intermediate reactor 25, and the composition and particle size of the primary precursor can be maintained. Therefore, even if the product generated in the first reactor 20 is stored in the intermediate reactor 25, the physical properties (e.g., particle size, etc.) of the first and second positive electrode active material precursors can be adjusted solely through the first reactor 20 and the second reactor 30.

[0116] The primary precursor prepared in the first reactor 20 is stored in the intermediate reactor 25. The primary precursor can be added to the second reactor 30 without exceeding the water level of the second reactor 30. Therefore, the yield of the first positive electrode active material precursor can be improved. For example, when the first reactor 20 is a batch reactor, the primary precursor prepared in the first reactor 20 can be discharged in batches. When the primary precursor is added to the second reactor 30 all at once, the water level of the second reactor 30 may be exceeded. Therefore, due to the batch addition of the primary precursor, the yield of the first positive electrode active material precursor in the second reactor 30 of the CSTR may decrease.

[0117] The term "above water level" as used in this invention can refer to a situation where the water level exceeds the optimal level for the reaction to proceed smoothly within the reactor, or a situation where the water level exceeds a pre-set predetermined level.

[0118] In some implementations, after the primary precursor is added to the second reactor 30 of the CSTR, the primary precursor can be grown into a first positive electrode active material precursor.

[0119] In some embodiments, adding the second transition metal source and the primary precursor to the second reactor 30 can simultaneously prepare the first positive electrode active material precursor (e.g., the shell portion of the first positive electrode active material precursor) and the second positive electrode active material precursor (e.g., process S30).

[0120] In one embodiment, when the second reactor 30 is a CSTR, a second positive electrode active material precursor can be prepared in the second reactor 30 together with the shell portion of the first positive electrode active material precursor. For example, when the second reactor 30 is a CSTR, a co-precipitation reaction of a second transition metal source can be carried out in the second reactor 30. Therefore, a transition metal layer can be further grown on the surface of the primary precursor to form the first positive electrode active material precursor. Furthermore, the core of the second positive electrode active material precursor can be formed and grown.

[0121] The coprecipitation reaction can be carried out at 40°C to 60°C, 45°C to 60°C, or 45°C to 55°C for 2 to 10 hours, 4 to 10 hours, or 4 to 8 hours. Furthermore, the coprecipitation reaction can be carried out with stirring at pH 9 to 12, 10 to 12, or 10 to 11 at 400 rpm to 1300 rpm, 600 rpm to 1300 rpm, or 600 rpm to 1000 rpm. Within the above ranges, the first positive electrode active material precursor can be grown to the aforementioned size.

[0122] In some embodiments, the first reactor 20 is a batch reactor, and the nickel content in the total weight of the first transition metal source can be less than the nickel content in the total weight of the second transition metal source. For example, the Ni content in the first transition metal source in the total weight of the first transition metal source can be less than the Ni content in the second transition metal source in the total weight of the second transition metal source.

[0123] For example, after preparing a primary precursor in the first reactor 20, a first positive electrode active material precursor can be prepared in a second reactor 30 where the nickel concentration is maintained at a higher level than that in the first reactor 20. Therefore, the average molar fraction of nickel in the second positive electrode active material precursor prepared in the second reactor 30 can be greater than the average molar fraction of nickel in the first positive electrode active material precursor. Furthermore, the relative content of Co in the second positive electrode active material precursor can be reduced. Therefore, the structural stability of the positive electrode active material formed from the first and second positive electrode precursors can be improved, and the ionic conductivity can be increased.

[0124] Figure 3 This is a schematic process flow diagram illustrating a method for preparing a positive electrode active material precursor according to an exemplary embodiment.

[0125] Reference Figure 3 The first reactor 20 can be a CSTR, and the second reactor 30 can be a batch reactor.

[0126] In some embodiments, when the first reactor 20 is a CSTR, a first primary precursor and a second primary precursor can be prepared in the first reactor 20 (e.g., process S15). For example, the first primary precursor can be the core of a first positive electrode active material precursor. For example, the second primary precursor can be the core of a second positive electrode active material precursor. For example, a co-precipitation reaction of a first transition metal source can be performed. Therefore, a first primary precursor and a second primary precursor can be formed.

[0127] The coprecipitation reaction can be carried out at 50°C to 70°C, 55°C to 70°C, or 55°C to 65°C for 6 to 15 hours, 8 to 15 hours, or 8 to 12 hours, respectively. The coprecipitation reaction can be carried out with stirring at pH 10 to 13, 10 to 12, or 11 to 12, at 500 rpm to 1500 rpm, 700 rpm to 1500 rpm, or 700 rpm to 1200 rpm. Within the above ranges, the sizes of the first and second primary precursors can be adjusted.

[0128] In some embodiments, the average particle size (D) of the first primary precursor and the second primary precursor is... 50 (They can be different.)

[0129] In some embodiments, the average particle size of the first primary precursor may be larger than that of the second primary precursor. For example, the average particle size of the first primary precursor may be the same as that of the primary precursor (e.g., 8 μm to 13 μm). For example, the average particle size of the second primary precursor may be smaller than that of the second positive electrode active material precursor. For example, the average particle size of the second primary precursor may be 1 μm to 4 μm, 2 μm to 3.5 μm, or 2 μm to 3 μm. For example, particles whose average particle size increases through particle growth starting from a seed at the initial stage of the reaction can be used as the first primary precursor. For example, particles generated after a certain period of time with relatively less particle growth can be used as the second primary precursor.

[0130] In some embodiments, when the first reactor 20 is a CSTR, the primary precursor and the second positive electrode active material precursor prepared in the first reactor 20 can be added to the intermediate reactor 25 (e.g., process S25). For example, the first primary precursor and the second primary precursor prepared in the first reactor 20 can be added to the intermediate reactor 25 through the first transfer path 23.

[0131] When the first reactor 20 is a CSTR, the transition metal source is continuously added to and discharged from the first reactor 20, and the prepared first and second primary precursors can also be discharged. The first and second primary precursors prepared in the first reactor 20 can be stored in the intermediate reactor 25. The addition rate of the first and second primary precursors can be adjusted according to the degree of reaction in the second reactor 30.

[0132] For example, depending on the degree of reaction in the second reactor 30, the first and second primary precursors stored in the intermediate reactor 25 can be added to the second reactor 30 via the second transfer path 27. Therefore, the yield from the primary precursors to the precursors can be increased.

[0133] Intermediate reactor 25 can be the same as the intermediate reactor 25 described above.

[0134] In some implementations, the first primary precursor and the second primary precursor are added together to a second reactor 30, which is a batch reactor, and then the first primary precursor can be grown into a first positive electrode active material precursor, and the second primary precursor can be grown into a second positive electrode active material precursor.

[0135] In some embodiments, the second transition metal source, the first primary precursor and the second primary precursor are added to the second reactor 30 to prepare the first positive electrode active material precursor (e.g., the shell of the first positive electrode active material precursor) and the second positive electrode active material precursor (e.g., process S35).

[0136] In one embodiment, when the second reactor 30 is a batch reactor, a shell may be formed only on the first primary precursor in the second reactor 30.

[0137] For example, when the second reactor 30 is a batch reactor, a further co-precipitation reaction of the second transition metal source can occur on the surface of the first primary precursor in the second reactor 30, thereby forming the first positive electrode active material precursor. For example, because the particle size of the second primary precursor is small, the second primary precursor cannot act as a nucleus, and the particles can grow uniformly. In addition, due to the size of the first primary precursor, the co-precipitation reaction can be concentrated on the first primary precursor, so the growth of the second primary precursor can be relatively smaller than the growth of the first primary precursor, thus forming a shell only on the first primary precursor.

[0138] The coprecipitation reaction can be carried out at 40°C to 60°C, 45°C to 60°C, or 45°C to 55°C for 4 to 20 hours, 7 to 20 hours, or 7 to 15 hours. The coprecipitation reaction can be carried out with stirring at pH 9 to 12, 10 to 12, or 10 to 11 at 400 rpm to 1300 rpm, 600 rpm to 1300 rpm, or 600 rpm to 1000 rpm. Within the above ranges, the first and second positive electrode active material precursors can be grown to the aforementioned dimensions.

[0139] For example, the first primary precursor formed in the first reactor 20 can essentially serve as the core of the first positive electrode active material precursor. Similarly, the transition metal layer further formed in the second reactor 30 can essentially serve as the shell of the first positive electrode active material precursor. Therefore, the first positive electrode active material precursor can have a core-shell structure.

[0140] In some embodiments, the first reactor 20 is a CSTR, and the nickel content in the total weight of the first transition metal source can be greater than the nickel content in the total weight of the second transition metal source. For example, the Ni content in the first transition metal source relative to the total weight of the first transition metal source can be greater than the Ni content in the second transition metal source relative to the total weight of the second transition metal source.

[0141] For example, after preparing a first primary precursor and a second primary precursor in a first reactor 20, in a second reactor 30 where the nickel concentration is maintained at a lower level than in the first reactor 20, the first primary precursor and the second primary precursor can be grown into a first positive electrode active material precursor and a second positive electrode active material precursor, respectively. Therefore, the average molar fraction of nickel contained in the second positive electrode active material precursor, which is less affected by the second transition metal source due to its smaller particle size, can be less than the average molar fraction of nickel contained in the first positive electrode active material precursor. Furthermore, the relative content of Co contained in the second positive electrode active material precursor can be increased. Therefore, the structural stability of the positive electrode active material formed from the first positive electrode precursor and the second positive electrode precursor can be improved, and the ionic conductivity can be increased.

[0142] Figure 4 and Figure 5 These are schematic plan views and schematic cross-sectional views illustrating a lithium secondary battery according to an exemplary embodiment. For example, Figure 5 It is along Figure 4 A cross-sectional view taken along the thickness direction of the I-I' line.

[0143] Reference Figure 4 and Figure 5The secondary battery may include a positive electrode 100 and a negative electrode 130 disposed opposite to the positive electrode 100. A separator 140 may be disposed between the positive electrode 100 and the negative electrode 130.

[0144] In some embodiments, the positive electrode 100 may include a positive electrode current collector 105 and a positive electrode active material layer 110 formed on at least one side of the positive electrode current collector 105.

[0145] The positive electrode current collector 105 may comprise stainless steel, nickel, aluminum, titanium, or alloys thereof. The positive electrode current collector 105 may also comprise aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. For example, the thickness of the positive electrode current collector 105 may be from 10 μm to 50 μm.

[0146] The positive electrode active material layer 110 may contain a positive electrode active material. According to an exemplary embodiment, the positive electrode active material may contain lithium transition metal oxide particles formed from the aforementioned positive electrode active material precursor.

[0147] In some embodiments, the first positive electrode active material precursor and the second positive electrode active material precursor can be mixed with a lithium precursor. The lithium precursor may include, for example, lithium carbonate, lithium nitrate, lithium acetate, lithium oxide, and lithium hydroxide, and two or more of them may be used alone or in combination.

[0148] Following the above mixing process, a positive electrode active material containing lithium transition metal oxide particles can be formed through a heat treatment process (e.g., calcination). This heat treatment can be carried out in an oxygen atmosphere at 650°C to 800°C. Within this range, the amount of lithium that might remain on the surface of the lithium transition metal oxide particles due to the high-temperature reaction can be reduced. Therefore, the lifespan and capacity characteristics of the secondary battery can be improved.

[0149] In some embodiments, the lithium transition metal oxide particles contained in the positive electrode active material may comprise a layered structure or a crystalline structure represented by the following chemical formula 2.

[0150] [Chemical Formula 2]

[0151] Li x Ni a M b O 2+z

[0152] In chemical formula 2, the values ​​can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, and -0.5≤z≤0.1. As mentioned above, M can contain Co, Mn, and / or Al.

[0153] The chemical structure represented by Formula 2 indicates the bonding relationships contained in the layered or crystalline structure of the positive electrode active material, and does not exclude other additional elements. For example, M may contain Co and / or Mn, and Co and / or Mn may be provided together with Ni as the main active elements of the positive electrode active material. Formula 2 is provided to represent the bonding relationships of the main active elements, and it should be understood that Formula 2 includes the introduction and substitution of additional elements.

[0154] In one embodiment, in addition to the primary active element, auxiliary elements may be further included to enhance the chemical stability of the positive electrode active material or the layered / crystal structure. These auxiliary elements may be incorporated into the layered / crystal structure to form a bond, and this should be understood to also include the chemical structures represented by Formula 2.

[0155] The auxiliary element may include at least one of, for example, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may function as an auxiliary active element, together with Co or Mn, to contribute to the capacity / power activity of the positive electrode active material; for example, Al.

[0156] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 2-1.

[0157] [Chemical Formula 2-1]

[0158] Li x Ni a M1 b01 M2 b02 O 2+z

[0159] In chemical formula 2-1, M1 may contain Co, Mn, and / or Al. M2 may contain the aforementioned auxiliary elements. In chemical formula 2-1, the values ​​can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b01+b02≤0.4, and -0.5≤z≤0.1.

[0160] The positive electrode active material may further include coating elements or doping elements. For example, elements that are substantially the same as or similar to the auxiliary elements described above can be used as coating elements or doping elements. For example, one or more combinations of the elements described above can be used as coating elements or doping elements.

[0161] The coating element or doping element may exist on the surface of the lithium transition metal oxide particles, or may penetrate through the surface of the lithium transition metal oxide particles and be included in the bonding structure represented by chemical formula 2 or chemical formula 2-1.

[0162] The positive electrode active material may contain nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, NCM-based lithium oxide with increased nickel content can be used.

[0163] Ni can be provided as a transition metal related to the power and capacity of lithium secondary batteries. Therefore, as described above, by using a high-content (high-Ni) composition in the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0164] However, with increasing Ni content, the long-term storage stability and lifetime stability of the cathode or secondary battery may relatively decrease, and side reactions with the electrolyte may also increase. However, according to an exemplary embodiment, conductivity can be maintained by including Co, while lifetime stability and capacity retention characteristics can be improved by including Mn.

[0165] The Ni content in the NCM-based lithium oxide (e.g., the mole fraction of nickel in the total moles of nickel, cobalt, and manganese) can be 0.6 or more, 0.7 or more, or 0.8 or more. For example, the Ni content can be from 0.8 to 0.95.

[0166] In some embodiments, the positive electrode active material may further include lithium cobalt oxide-based active material, lithium manganese oxide-based active material, lithium nickel oxide-based active material, or lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0167] In some embodiments, the positive electrode active material may further include, for example, lithium-rich layered oxide (LLO) / over-lithiated oxide (OLO) based active materials, manganese-rich based active materials, and cobalt-less based active materials having a chemical structure or crystal structure represented by Formula 3.

[0168] [Chemical Formula 3]

[0169] p[Li₂MnO₃]·(1-p)[Li q JO2]

[0170] In Chemical Formula 3, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J may contain at least one element selected from Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0171] The positive electrode active material may be mixed in a solvent to prepare a positive electrode paste. The positive electrode paste may be coated on the positive electrode current collector 105 and then dried and calendered to prepare the positive electrode active material layer 110. The coating may include methods such as gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc. The positive electrode active material layer 110 may further contain a binder and may optionally further contain a conductive material, a thickener, etc.

[0172] The solvent may be N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0173] The binder may include polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) copolymer, polyacrylonitrile, polymethyl methacrylate, nitrile rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. These may be used alone or in combination of two or more.

[0174] The conductive material may be added to enhance the conductivity and / or the migration of lithium ions or electrons in the positive electrode active material layer 110. For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, etc. and / or metal-based conductive materials including perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc. These may be used alone or in combination of two or more.

[0175] The positive electrode paste may further include a thickening agent and / or a dispersing agent, etc. In one embodiment, the positive electrode paste may include a thickening agent such as carboxymethyl cellulose (CMC).

[0176] The negative electrode 130 may include a negative electrode current collector 125 and a negative electrode active material layer 120 provided on at least one surface of the negative electrode current collector 125.

[0177] For example, the negative electrode current collector 125 may include a copper foil, a nickel foil, a stainless steel foil, a titanium foil, a foam nickel, a foam copper, a polymer substrate coated with a conductive metal, etc. For example, the thickness of the negative electrode current collector 125 may be 10 μm to 50 μm.

[0178] The negative electrode active material layer 120 may contain a negative electrode active material. The negative electrode active material may be a material that allows lithium ions to be intercalated and deintercalated. For example, the negative electrode active material may use carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers; lithium metal; lithium alloys; silicon (Si)-containing substances or tin (Sn)-containing substances, etc.

[0179] Examples of the amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0180] Examples of the crystalline carbon may include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, graphitized MPCF, etc.

[0181] The lithium metal may include pure lithium metal or lithium metal formed with a protective layer for suppressing dendrite growth, etc. In one embodiment, a layer containing lithium metal deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one embodiment, a lithium thin film layer may be used as the negative electrode active material layer.

[0182] As the elements contained in the lithium alloy, aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium or indium, etc. may be cited.

[0183] The silicon-containing substance may provide further enhanced capacity characteristics. The silicon-containing substance may include Si, SiO x (0 < x < 2), SiO doped with a metal x (0 < x < 2), silicon-carbon composites, etc. The metal may include lithium and / or magnesium, and SiO doped with a metal x (0 < x < 2) may include metal silicate.

[0184] For example, the negative electrode active material can be mixed in a solvent to prepare a negative electrode slurry. The negative electrode slurry can be coated / deposited onto the negative electrode current collector 125 and then dried and calendered to prepare the negative electrode active material layer 120. The coating process can be performed by methods such as gravure coating, slot die coating, multilayer simultaneous die coating, embossing, blade coating, dip coating, rod coating, and casting, and is not limited to these methods. The negative electrode active material layer 120 may further contain a binder and may further contain conductive materials, thickeners, etc.

[0185] In some embodiments, the negative electrode 130 may further include a negative electrode active material layer 120 in the form of lithium metal formed by a deposition / coating process.

[0186] Non-limiting examples of solvents used as the negative electrode active material layer include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, tert-butanol, etc.

[0187] The aforementioned substances, which can be used in the manufacture of the positive electrode, can be used as the adhesive, conductive material, and thickener.

[0188] In some implementations, the negative electrode adhesive can be a styrene-butadiene-rubber (SBR) based adhesive, a carboxymethyl cellulose (CMC) based adhesive, a polyacrylic acid based adhesive, a poly(3,4-ethylenedioxythiophene) (PEDOT) based adhesive, etc.

[0189] A diaphragm 140 can be provided between the positive electrode 100 and the negative electrode 130. The diaphragm 140 can be configured to prevent short circuits between the positive electrode 100 and the negative electrode 130 and to generate ion flow.

[0190] For example, the diaphragm 140 may comprise a porous polymer membrane or a porous nonwoven fabric. The porous polymer membrane may comprise polyolefin-based polymers such as ethylene polymers, propylene polymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers. These may be used alone or in combination of two or more. The porous nonwoven fabric may comprise high-melting-point glass fibers, polyethylene terephthalate fibers, etc. The diaphragm 140 may also comprise a ceramic-based material. For example, inorganic particles may be coated on or dispersed within the polymer membrane to improve heat resistance.

[0191] The diaphragm 140 may have a single-layer or multi-layer structure comprising the aforementioned polymer membrane and / or nonwoven fabric.

[0192] According to an exemplary embodiment, the battery cell can be defined by a positive electrode 100, a negative electrode 130, and a separator 140, and an electrode assembly 150 can be formed, for example, in a jelly roll form, by stacking multiple battery cells. For example, the electrode assembly 150 can be formed by winding, stacking, z-folding, stack-folding, etc., of the separator 140.

[0193] The electrode assembly 150 can be housed together with the electrolyte in the housing 160, thereby defining a lithium secondary battery. According to an exemplary embodiment, the electrolyte can be a non-aqueous electrolyte.

[0194] The non-aqueous electrolyte contains a lithium salt and an organic solvent, the lithium salt being, for example, Li... + X - This indicates that the anion (X) of the lithium salt is... - ), can be exemplified by F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF -, (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , (CF3CF2SO2)2N - etc.

[0195] The organic solvent may be, for example, propylene carbonate (PC), ethylene carbonate (EC), butene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, vinylene carbonate, methyl acetate (MA), ethyl acetate (EA), n-propylacetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), ethyl fluoroacetate (FEA), ethyl difluoroacetate (DFEA), ethyl trifluoroacetate (TFEA), dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), and diethylene glycol dimethyl ether. These include ether (DEGDME), tetrahydrofuran (THF), 2-methyltetrahydrofuran, ethyl alcohol, isopropyl alcohol, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, γ-butyrolactone, propylene sulfite, etc. These can be used alone or in combination of two or more.

[0196] The non-aqueous electrolyte may further contain additives. These additives may include, for example, cyclic carbonate compounds, fluorinated carbonate compounds, sulfonyl lactone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, borate compounds, etc. These may be used alone or in combination of two or more.

[0197] The cyclic carbonate-based compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc.

[0198] The fluorinated carbonate compounds may include fluoroethylene carbonate (FEC), etc.

[0199] The sulfonyl compounds may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc.

[0200] The cyclic sulfate-based compounds may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc.

[0201] The cyclic sulfite-based compounds may include ethylene sulfite, butylene sulfite, etc.

[0202] The phosphate-based compounds may include lithium difluorobis-oxalato phosphate, lithium difluorophosphate, etc.

[0203] The borate-based compounds may include lithium bis(oxalate) borate, etc.

[0204] like Figure 5 As shown, the tabs (positive tab and negative tab) can protrude from the positive current collector 105 and negative current collector 125 belonging to each cell and extend to one side of the housing 160. The tabs can be fused to said side of the housing 160 to form electrode leads (positive lead 107 and negative lead 127) extending to or exposed outside the housing 160.

[0205] The lithium secondary battery can be manufactured in shapes such as cylindrical, prismatic, pouch, or coin, for example, using a can.

[0206] The embodiments of the present invention will be further described below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are only for illustrating the present invention and are not intended to limit the scope of the claims. Various changes and modifications can be made to the embodiments within the scope of the present invention and its technical concept, which is obvious to those skilled in the art, and such variations and modifications naturally fall within the scope of the claims.

[0207] Examples and Comparative Examples

[0208] Example 1

[0209] (1) Preparation of positive electrode active material precursor

[0210] In a first transition metal storage container, NiSO4, CoSO4 and MnSO4 are added in a molar ratio of 86:7:7, and then water is added to prepare a first transition metal source.

[0211] The first transition metal source is added to a batch reactor, and stirring is performed while continuously supplying N2 gas as an inert gas, NH4OH as a chelating agent, and NaOH as a pH adjuster, thereby preparing a Ni-containing reactor. 0.86 Co 0.07 Mn 0.07 Primary precursors composed of (OH)2.

[0212] The average particle size (D) of the primary precursor 50 The value is 10μm.

[0213] The prepared primary precursor is added to the intermediate reactor.

[0214] In a second transition metal storage container, NiSO4, CoSO4 and MnSO4 are added in a molar ratio of 95:4:1, and then water is added to prepare a second transition metal source.

[0215] The second transition metal source and the primary precursor are added to a continuous stirred tank reactor (CSTR), and stirring is performed while continuously supplying N2 gas as an inert gas, NH4OH as a chelating agent, and NaOH as a pH adjuster, thereby preparing a Ni-containing product. 0.92 Co 0.05 Mn 0.03 The first positive electrode active material precursor composed of (OH)2 and having Ni 0.95 Co 0.04 Mn 0.01 The precursor of the second positive electrode active material composed of (OH)2.

[0216] The average particle size (D) of the first positive electrode active material precursor 50 The average particle size (D) of the second positive electrode active material precursor is 15 μm. 50 The value is 4.5 μm.

[0217] The average particle size (D) 50The calculation is as follows: The primary precursor, the first positive electrode active material precursor, and the second positive electrode active material precursor are dispersed in a dispersion medium (10% by weight of an aqueous dispersion of sodium hexametaphosphate (NaPO3)6). The difference in diffraction patterns based on particle size is then measured using a Microtrac MT 3000 laser diffractometer to calculate the average particle size (D). 50 ).

[0218] (2) Preparation of positive electrode active material

[0219] Lithium hydroxide (LiOH), used as the lithium source, was calcined at 750°C in an oxygen atmosphere for 10 hours. The calcined lithium source, the first positive electrode active material precursor, and the second positive electrode active material precursor were mixed in a molar ratio of 2.1:1:1, and then calcined at 765°C in an oxygen atmosphere for 20 hours. After that, the mixture was pulverized, washed with water, and then calcined at 300°C to prepare the positive electrode active material in the form of lithium transition metal oxide particles.

[0220] (3) Manufacturing of lithium secondary batteries

[0221] The positive electrode active material, acetylene black (Denka Black) as a conductive material, and PVDF as a binder are mixed in a mass ratio of 92:5:3 to prepare a positive electrode slurry.

[0222] The positive electrode slurry is coated onto an aluminum current collector, and then dried and rolled to manufacture the positive electrode.

[0223] A negative electrode slurry is prepared, comprising 95% by weight of a negative electrode active material composed of a mixture of artificial graphite and natural graphite in a 7:3 weight ratio, 1% by weight of Super-P as a conductive material, 2% by weight of styrene-butadiene rubber (SBR) as a binder, and 2% by weight of carboxymethyl cellulose (CMC) as a thickener. The negative electrode slurry is uniformly coated onto copper foil, and then dried and calendered to manufacture the negative electrode.

[0224] The positive and negative electrodes manufactured as described above are cut to specified dimensions and stacked. A separator (polyethylene, 15 μm thick) is placed between the positive and negative electrodes to form a battery cell. The tab portions of the positive and negative electrodes are welded together. The welded positive / separator / negative electrode assembly is placed in a soft case, and the three sides except for the electrolyte injection surface are sealed. Furthermore, the portion with the tabs is included in the sealed area. Electrolyte is injected through the remaining surfaces except for the sealed areas, the remaining surfaces are sealed, and then the battery is immersed for at least 12 hours to manufacture a lithium secondary battery.

[0225] The electrolyte uses a mixed solvent of EC / EMC / DEC (volume ratio of 25 / 45 / 30), with 3% by weight of fluoroethylene carbonate (FEC), 1% by weight of 1,3-propenyl sulpholol (PRS), and 0.5% by weight of lithium bis(oxalate)borate (LiBOB) added to a 1M LiPF6 solution relative to the total weight of the electrolyte.

[0226] Then, pre-charge for 36 minutes at the current (2.5A) corresponding to 0.25C. After 1 hour, degassing and aging for at least 24 hours are performed, followed by formation charge-discharge (charging conditions: CC-CV 0.2C 4.2V 0.05C cut-off, discharging conditions: CC 0.2C 2.5V cut-off). Afterwards, standard charge-discharge is performed (charging conditions: CC-CV 0.5C 4.2V 0.05C cut-off, discharging conditions: CC 0.5C 2.5V cut-off).

[0227] Examples 2 to 6

[0228] The positive electrode active material and lithium secondary battery were prepared using the same method as in Example 1, except that the contents of NiSO4, CoSO4, and MnSO4 in the first and second transition metal sources were changed, and the composition and average particle size (D) of the primary precursor, the first positive electrode active material precursor, and the second positive electrode active material precursor were varied according to Tables 1 and 2 below. 50 ).

[0229] Example 7

[0230] The positive electrode active material and lithium secondary battery were prepared using the same method as in Example 1, except that the positive electrode active material precursor was prepared as follows.

[0231] Preparation of positive electrode active material precursor

[0232] In a first transition metal storage container, NiSO4, CoSO4 and MnSO4 are added in a molar ratio of 96:2:2, and then water is added to prepare a first transition metal source.

[0233] The first transition metal source is added to the CSTR, and the mixture is stirred while continuously supplying N2 gas as an inert gas, NH4OH as a chelating agent, and NaOH as a pH adjuster, thereby preparing a product with Ni 0.96 Co 0.02 Mn 0.02 The first primary precursor has the composition of (OH)2. Furthermore, a Ni-containing precursor is prepared. 0.96 Co 0.02 Mn0.02 The second primary precursor composed of (OH)2.

[0234] The average particle size (D) of the first primary precursor 50 The average particle size (D) of the second primary precursor is 10 μm. 50 The value is 3.0 μm.

[0235] The first and second primary precursors obtained are added to the intermediate reactor.

[0236] In a second transition metal storage container, NiSO4, CoSO4 and MnSO4 are added in a molar ratio of 90:6:4, and then water is added to prepare a second transition metal source.

[0237] The second transition metal source and the aforementioned primary precursor are added to a batch reactor, and stirring is performed while continuously supplying N2 gas as an inert gas, NH4OH as a chelating agent, and NaOH as a pH adjuster, thereby preparing a Ni-containing... 0.92 Co 0.05 Mn 0.03 The first positive electrode active material precursor composed of (OH)2 and having Ni 0.91 Co 0.06 Mn 0.03 The precursor of the second positive electrode active material composed of (OH)2.

[0238] The average particle size (D) of the first positive electrode active material precursor 50 The average particle size (D) of the second positive electrode active material precursor is 15 μm. 50 The value is 4.5 μm.

[0239] Examples 8 to 12

[0240] The positive electrode active material and lithium secondary battery were prepared using the same method as in Example 7, except that the contents of NiSO4, CoSO4, and MnSO4 in the first and second transition metal sources were changed, and the composition and average particle size (D) of the first primary precursor, the first positive electrode active material precursor, and the second positive electrode active material precursor were varied according to Tables 1 and 2 below. 50 ).

[0241] Comparative Example 1

[0242] The lithium secondary battery was manufactured using the same method as in Example 1, except that the contents of NiSO4, CoSO4, and MnSO4 in the first and second transition metal sources, the stirring conditions, etc., were changed, and the composition and average particle size (D) of the primary precursor, the first positive electrode active material precursor, and the second positive electrode active material precursor were changed according to Tables 1 and 2 below. 50 ).

[0243] Comparative Example 2

[0244] The lithium secondary battery was manufactured using the same method as in Example 7, except that the contents of NiSO4, CoSO4, and MnSO4 in the first and second transition metal sources, the stirring conditions, etc., were changed, and the composition and average particle size (D) of the primary precursor, the first positive electrode active material precursor, and the second positive electrode active material precursor were changed according to Tables 1 and 2 below. 50 ).

[0245] Comparative Example 3

[0246] The positive electrode active material and lithium secondary battery were prepared using the same method as in Example 1, except that the positive electrode active material precursor was prepared as follows.

[0247] Preparation of positive electrode active material precursor

[0248] A transition metal source was prepared by adding NiSO4, CoSO4 and MnSO4 in a molar ratio of 89.5:6.5:4 to a transition metal storage container, followed by the addition of water.

[0249] The transition metal source is added to the CSTR, and the mixture is stirred while continuously supplying N2 gas as an inert gas, NH4OH as a chelating agent, and NaOH as a pH adjuster, thereby preparing a product with Ni 0.895 Co 0.065 Mn 0.040 The first positive electrode active material precursor and the second positive electrode active material precursor are composed of (OH)2.

[0250] The second positive electrode active material precursor has an average particle size (D) of 4.5 μm. 50 The first positive electrode active material precursor was collected during the process of having an average particle size (D) of 15 μm. 50 Collected at that time.

[0251] Comparative Examples 4 to 6

[0252] The lithium secondary battery was manufactured using the same method as in Comparative Example 3, except that the composition of the first positive electrode active material precursor and the second positive electrode active material precursor was changed by altering the contents of NiSO4, CoSO4 and MnSO4 contained in the first transition metal source and the second transition metal source, as shown in Table 1 below.

[0253] Comparative Example 7

[0254] The lithium secondary battery was manufactured using the same method as in Example 1, except that the positive electrode active material precursor was prepared as follows.

[0255] Preparation of positive electrode active material precursor

[0256] A first transition metal source was prepared by adding NiSO4, CoSO4, and MnSO4 in a molar ratio of 92:5:3 to a transition metal storage container, followed by the addition of water. A second transition metal source was prepared by adding NiSO4, CoSO4, and MnSO4 in a molar ratio of 89.5:6.5:4 to a transition metal storage container, followed by the addition of water.

[0257] The aforementioned transition metal source was added to a first batch reactor and a second batch reactor, respectively. Stirring was performed while continuously supplying N2 gas as an inert gas, NH4OH as a chelating agent, and NaOH as a pH adjuster. In the first batch reactor, a Ni-containing... 0.92 Co 0.05 Mn 0.03 The first positive electrode active material precursor, composed of (OH)2, is prepared in the second batch reactor to produce Ni 0.895 Co 0.065 Mn 0.04 The precursor of the second positive electrode active material composed of (OH)2.

[0258] The average particle size (D) of the first positive electrode active material precursor 50 The average particle size (D) of the second positive electrode active material precursor is 15 μm. 50 The value is 4.5 μm.

[0259] Comparative Example 8

[0260] The lithium secondary battery was manufactured using the same method as in Comparative Example 7, except that the composition of the first positive electrode active material precursor and the second positive electrode active material precursor was changed by altering the contents of NiSO4, CoSO4 and MnSO4 contained in the first transition metal source and the second transition metal source, as shown in Table 1 below.

[0261] Comparative Example 9

[0262] The lithium secondary battery was manufactured using the same method as in Example 1, except that the positive electrode active material precursor was prepared as follows.

[0263] Preparation of positive electrode active material precursor

[0264] A first transition metal source was prepared by adding NiSO4, CoSO4, and MnSO4 in a molar ratio of 92:5:3 to a transition metal storage container, followed by the addition of water. A second transition metal source was prepared by adding NiSO4, CoSO4, and MnSO4 in a molar ratio of 89.5:6.5:4 to a transition metal storage container, followed by the addition of water.

[0265] The transition metal source is added to the first batch reactor and the second batch reactor, respectively. While continuously supplying N2 gas as an inert gas, NH4OH as a chelating agent and NaOH as a pH adjuster, the mixture is stirred to carry out a co-precipitation reaction, thereby preparing intermediate products.

[0266] The transition metal source is further added to the first batch reactor, and further added to the second batch reactor. Then, while continuously supplying N2 gas as an inert gas, NH4OH as a chelating agent, and NaOH as a pH adjuster, stirring is performed to prepare a Ni-containing product in the first batch reactor. 0.92 Co 0.05 Mn 0.03 The first positive electrode active material precursor, composed of (OH)2, is prepared in the second batch reactor to produce Ni 0.895 Co 0.065 Mn 0.04 The precursor of the second positive electrode active material composed of (OH)2.

[0267] The average particle size (D) of the first positive electrode active material precursor 50 The average particle size (D) of the second positive electrode active material precursor is 15 μm. 50 The value is 4.5 μm.

[0268] Comparative Example 10

[0269] The lithium secondary battery was manufactured using the same method as Comparative Example 9, except that the composition of the first positive electrode active material precursor and the second positive electrode active material precursor was changed by altering the contents of NiSO4, CoSO4 and MnSO4 contained in the first transition metal source and the second transition metal source, as shown in Table 1 below.

[0270] [Table 1]

[0271]

[0272] [Table 2]

[0273]

[0274] Experimental Example

[0275] (1) Evaluation of initial capacity efficiency

[0276] The lithium secondary batteries prepared according to the examples and comparative examples were subjected to one charge (CC-CV 0.1C 0.01V 0.01C cutoff) and one discharge (CC 0.1C 1.5V cutoff) at room temperature (25°C) to measure the initial charge capacity and initial discharge capacity.

[0277] The initial capacity efficiency is calculated as a percentage of the measured initial discharge capacity relative to the initial charge capacity.

[0278] Initial capacity efficiency (%) = (Initial discharge capacity / Initial charge capacity) × 100

[0279] (2) Evaluation of lifespan characteristics at room temperature (25℃)

[0280] The lithium secondary batteries prepared according to the examples and comparative examples were charged (CC-CV 0.5C 4.2V 0.05C cutoff) and discharged (CC 0.5C 2.75V cutoff), and the 50th discharge capacity relative to the first discharge capacity was calculated as a percentage, thereby measuring the room temperature lifetime characteristics.

[0281] Room temperature capacity retention rate (%) = (50th discharge capacity / 1st discharge capacity) × 100

[0282] The evaluation results are shown in Table 3 below.

[0283] [Table 3]

[0284]

[0285] As shown in Table 3, when using both CSTR and batch reactors, and with the primary precursor's average particle size (D... 50 The average particle size (D) of the precursor material for the second positive electrode is greater than that of the precursor material for the second positive electrode. 50 In the embodiments of ), the room temperature capacity retention rate is above 89.4%.

[0286] In the comparative example using only CSTR or batch reactor, the ambient temperature life characteristics were reduced.

Claims

1. A precursor for a positive electrode active material used in lithium secondary batteries, comprising: First positive electrode active material precursor particles, the first positive electrode active material precursor particles comprising a core and a shell, the core and shell comprising a nickel-containing transition metal; and The second positive electrode active material precursor particles contain a nickel-containing transition metal. in, In the transition metal of the second positive electrode active material precursor particles, the molar fraction of nickel remains constant throughout the entire second positive electrode active material precursor particles. The average particle size D of the core of the first positive electrode active material precursor particle 50 The average particle size D of the second positive electrode active material precursor particles is greater than that of the second positive electrode active material precursor particles. 50 .

2. The precursor for positive electrode active material in lithium secondary batteries according to claim 1, wherein, The average particle size D of the core 50 The size ranges from 8μm to 13μm.

3. The precursor for positive electrode active material in lithium secondary batteries according to claim 1, wherein, The average particle size D of the second positive electrode active material precursor particles 50 The size ranges from 3μm to 6μm.

4. The precursor for positive electrode active material in lithium secondary batteries according to claim 1, wherein, The average molar fraction of nickel in the transition metal of the first positive electrode active material precursor particles is greater than the average molar fraction of nickel in the transition metal of the second positive electrode active material precursor particles.

5. The precursor for positive electrode active material in lithium secondary batteries according to claim 1, wherein, The transition metal further comprises cobalt and manganese.

6. A positive electrode active material for lithium secondary batteries, comprising lithium transition metal oxide particles formed from the precursor of the positive electrode active material for lithium secondary batteries according to claim 1.

7. A lithium secondary battery, comprising: The positive electrode comprises the positive electrode active material for lithium secondary batteries as described in claim 6; negative electrode; as well as A diaphragm is disposed between the positive electrode and the negative electrode.

8. A method for preparing a positive electrode active material precursor for lithium secondary batteries, comprising the following steps: A nickel-containing first transition metal source is added to the first reactor to prepare a primary precursor; The primary precursor and a nickel-containing second transition metal source are added to the second reactor to prepare a first positive electrode active material precursor with a core-shell structure. as well as In one or more of the first and second reactors, a second positive electrode active material precursor with a uniform nickel content throughout the particles is prepared. The first reactor and the second reactor are respectively a continuous stirred tank reactor (CSTR) or a batch reactor, and the first reactor and the second reactor are different from each other.

9. The method for preparing the positive electrode active material precursor for lithium secondary batteries according to claim 8, wherein, The first reactor is the batch reactor, and the second reactor is the continuous stirred tank reactor (CSTR). The steps of preparing the second positive electrode active material precursor and preparing the first positive electrode active material precursor in the second reactor are performed simultaneously.

10. The method for preparing the positive electrode active material precursor for lithium secondary batteries according to claim 9, wherein, The steps of preparing the second positive electrode active material precursor and the formation of the shell portion of the first positive electrode active material precursor are performed simultaneously.

11. The method for preparing the positive electrode active material precursor for lithium secondary batteries according to claim 8, wherein, The first reactor is a continuous stirred tank reactor (CSTR), and the second reactor is a batch reactor. The step of preparing the primary precursor includes preparing an average particle size D in the first reactor. 50 The first and second primary precursors are different from each other. The step of preparing the second positive electrode active material precursor includes adding the second primary precursor and the second transition metal source into the second reactor to prepare the second positive electrode active material precursor.

12. The method for preparing the positive electrode active material precursor for lithium secondary batteries according to claim 11, wherein, The first primary precursor and the second primary precursor prepared in the first reactor are added together into the second reactor. The step of preparing the first positive electrode active material precursor includes forming a shell only on the first primary precursor added to the second reactor.

13. The method for preparing the positive electrode active material precursor for lithium secondary batteries according to claim 8, wherein, The first reactor is a continuous stirred tank reactor (CSTR), and the nickel content in the total weight of the first transition metal source is greater than the nickel content in the total weight of the second transition metal source.

14. The method for preparing the positive electrode active material precursor for lithium secondary batteries according to claim 8, wherein, The first reactor is a batch reactor, and the nickel content in the total weight of the first transition metal source is less than the nickel content in the total weight of the second transition metal source.

15. The method for preparing the positive electrode active material precursor for lithium secondary batteries according to claim 8, wherein, The preparation method further includes the step of adding the primary precursor to an intermediate reactor before adding the primary precursor to the second reactor.

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