KR20220089412A - Cathode active material, and lithium ion battery including the same - Google Patents

Abstract

The present embodiments include a large particle diameter positive active material having an average particle diameter in the range of 7 μm to 11 μm, and a small positive electrode active material having an average particle diameter in a range of 3 μm to 5 μm, wherein the large particle diameter positive electrode active material and the small particle diameter positive active material The bimodal positive active material comprising: when pressurized to 1.75 tons using pressurization equipment, provides a positive electrode active material having a particle size retention rate of 60% or more based on D5 before/after pressurization.

Description

A cathode active material and a lithium secondary battery comprising the same {CATHODE ACTIVE MATERIAL, AND LITHIUM ION BATTERY INCLUDING THE SAME}

The present embodiments relate to a cathode active material and a lithium secondary battery including the same.

Recently, thanks to the explosive increase in demand for IT mobile devices and small electric power devices (e-bikes, small EVs, etc.) and the development of electric and hybrid vehicles, the technology development for lithium secondary batteries to drive them is actively progressing worldwide. have.

In order to realize a high energy type lithium ion secondary battery having a voltage of 4V, various positive electrode active materials have been proposed, and among them, a lithium ion secondary battery using LiNiO ₂ is attracting attention as a battery having a high charge/discharge capacity. However, LiNiO ₂ positive electrode active material has a problem in that the thermal stability during charging and durability according to the charge/discharge cycle is inferior.

Therefore, there is a need for development of a positive electrode active material having high energy density and excellent high temperature life and high temperature storage characteristics, which are long-term reliability characteristics.

In this embodiment, an object of the present invention is to provide a positive active material for a lithium secondary battery with significantly improved high temperature lifespan and storage characteristics.

A positive active material according to an embodiment may include a large particle diameter positive active material having an average particle diameter in the range of 7 μm to 11 μm; and a small particle diameter positive active material having an average particle diameter in the range of 3 μm to 5 μm; including, wherein the bimodal positive active material including the large particle diameter positive active material and the small particle diameter positive active material was pressurized to 1.75 tons using pressurization equipment At this time, the particle size retention before/after pressurization may be 60% or more based on D5.

When the bimodal positive active material is pressurized to 1.75 tons using a pressurizing device, the particle size retention rate before/after pressurization may be 65% or more based on D10.

When the large particle diameter positive electrode active material is pressurized to 2.0 tons using a pressurizing device, the particle size retention rate before/after pressurization may be 85% or more based on D5.

When the large particle diameter positive electrode active material is pressurized to 2.0 tons using a pressurizing device, the particle size retention rate before/after pressurization may be 89% or more based on D10.

When the small particle size positive electrode active material is pressurized to 1.75 tons using a pressurization device, the particle size retention rate before/after pressurization may be 70% or more based on D50.

The particle strength of the large-diameter positive electrode active material may be 140Mpa or more.

A mixing ratio of the large particle diameter positive electrode active material and the small particle diameter positive electrode active material may be in the range of 9: 1 to 6: 4 by weight.

The bimodal positive electrode active material may be in the form of secondary particles each including a plurality of primary particles.

The average particle diameter of the primary particles may be in the range of 0.1 μm to 1 μm.

The positive active material may include a compound represented by Formula 1 below.

[Formula 1]

Li _1+m Ni _1-wxyz Co _w Mn _x M1 _y M2 _z O _2-p X _p

(In Formula 1, M1 and M2 are different from each other, and Al, Mg, Zr, Sn, Ca, Ge, Ti, Cr, Fe, Zn, Y, Ba, La, Ce, Sm, Gd, Yb, Sr, Any one element selected from the group consisting of Cu and Ga,

X is any one element selected from the group consisting of F, N, S, and P, and w, x, y, z, p and m are each 0.125<w<0.202, 0.153<x<0.225, 0=y= 0.1, 0=z=0.1, 0.34=w+x=0.36, 0=p=0.1, -0.1=m=0.2)

The content of Li ₂ CO ₃ remaining on the surface of the positive active material may be in the range of 1,500 ppm to 5,000 pm.

Since particle deformation of the positive active material according to the present embodiment is minimized even when a pressure in a certain range is applied, when applied to a lithium secondary battery, high temperature lifespan and storage characteristics can be remarkably improved.

The terms first, second and third etc. are used to describe, but are not limited to, various parts, components, regions, layers and/or sections. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

The terminology used herein is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and includes the presence or absence of another characteristic, region, integer, step, operation, element and/or component. It does not exclude additions.

When a part is referred to as being “on” or “on” another part, it may be directly on or on the other part, or the other part may be involved in between. In contrast, when a part is referred to as being "directly above" another part, the other part is not interposed therebetween.

Although not defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Commonly used terms defined in the dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and unless defined, are not interpreted in an ideal or very formal meaning.

In addition, unless otherwise specified, % means weight %, and 1 ppm is 0.0001 weight %.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement them. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

The positive electrode active material for a lithium secondary battery according to an embodiment includes a large particle diameter positive electrode active material having an average particle diameter in the range of 7 μm to 11 μm, and a small particle diameter positive electrode active material having an average particle diameter in the range of 3 μm to 5 μm, wherein the large particle diameter positive electrode When the bimodal positive active material including the active material and the small particle diameter positive active material is pressurized to 1.75 tons using a pressurizing device, the particle size retention rate before/after the pressurization may be 60% or more based on D5.

The positive electrode active material of this embodiment may have a bimodal shape including the large particle diameter positive electrode active material and the small particle diameter positive electrode active material.

When the bimodal positive active material is pressurized to 1.75 tons using a pressurizing device, the particle size retention rate before/after pressurization is 60% or more based on D5, more specifically 60% to 65%, or 60% to 64% range can be When the D5 particle size retention ratio of the bimodal positive active material satisfies the above range, particle deformation due to slip between particles due to the high sphericity of the large and small particle diameter positive active material during bimodalization can be alleviated. In addition, since it has high strength characteristics, when the electrode is manufactured using the positive active material of this embodiment, the rolling rate can be improved, and thus, a lithium secondary battery having a high energy density can be realized.

In addition, the bimodal positive active material, when pressurized to 1.75 tons using a pressurization device, the particle size retention before/after pressurization is 65% or more, more specifically 65% to 71%, or 65% to 70% based on D10. % range. When the D10 particle size retention ratio of the bimodal positive active material satisfies the above range, particle deformation due to slip between particles due to the high sphericity of the large and small particle diameter positive active material during bimodalization can be alleviated. In addition, since it has high strength characteristics, when the electrode is manufactured using the positive active material of this embodiment, the rolling rate can be improved, and thus, a lithium secondary battery having a high energy density can be realized.

When the small particle size positive electrode active material is pressurized to 1.75 tons using a pressurization device, the particle size retention rate before/after pressurization may be 70% or more based on D50.

In this embodiment, when the small particle diameter positive active material is pressurized to 1.75 tons using a pressurizing device, the particle size retention before/after pressurization is 70% or more based on D50, more specifically 70% to 73% or 70% to 72% range. When the D50 particle size retention ratio of the small particle diameter positive active material satisfies the above range, particle deformation due to slip between particles due to the high sphericity of the small particle diameter positive active material during bimodalization with the large particle diameter active material can be alleviated. In addition, since it has high strength characteristics, when the electrode is manufactured using the positive active material of this embodiment, the rolling rate can be improved, and thus, a lithium secondary battery having a high energy density can be realized.

The large particle size positive electrode active material, when pressurized to 2.0 tons using a pressurizing device, has a particle size retention rate of 85% or more, more specifically 85% to 91%, or 85% to 90%, based on D5, before and after pressurization. can be When the particle size retention rate of the large-diameter positive active material satisfies the above range, particle deformation due to slip between particles due to the high sphericity of the large-diameter positive active material during bimodalization with the small particle size active material can be alleviated. In addition, since it has high strength characteristics, when the electrode is manufactured using the positive active material of this embodiment, the rolling rate can be improved, and thus, a lithium secondary battery having a high energy density can be realized.

The large particle size positive electrode active material, when pressurized to 2.0 tons using a pressurization device, the particle size retention before and after pressurization is 89% or more based on D10, more specifically 89% to 93% or 89% to 92% range can When the particle size retention rate of the large-diameter positive active material satisfies the above range, particle deformation due to slip between particles due to the high sphericity of the large-diameter positive active material during bimodalization with the small particle size active material can be alleviated. In addition, since it has high strength characteristics, when the electrode is manufactured using the positive active material of this embodiment, the rolling rate can be improved, and thus, a lithium secondary battery having a high energy density can be realized.

Meanwhile, the particle strength of the large-diameter positive electrode active material may be 140 Mpa or more, more specifically, 140 Mpa to 143 Mpa, or 140 Mpa to 142 Mpa. When the particle strength of the large particle diameter positive electrode active material satisfies the above range, particle deformation can be alleviated and high strength characteristics can be realized.

The large particle diameter positive electrode active material of this embodiment may be derived from a large particle diameter positive electrode precursor having a particle strength in the range of 81 Mpa to 86 Mpa.

In the bimodal positive active material of this embodiment, the mixing ratio of the large-diameter positive active material and the small-diameter positive active material may be in the range of 9: 1 to 6: 4 or 8: 2 to 7: 3 by weight. When the mixing ratio of the large particle diameter and the small particle diameter positive electrode active material satisfies the above range, the rolling rate can be improved during electrode manufacturing, so that a lithium secondary battery having high energy density and high output characteristics can be realized.

Meanwhile, in this embodiment, the bimodal positive active material may be secondary particles including a plurality of primary particles.

In this case, the average particle diameter of the primary particles may be in the range of 0.1 μm to 1 μm. When the average particle diameter of the primary particles satisfies the above range, the effect of improving lithium ion mobility according to the primary particle size and improving battery performance can be expected.

In addition, in the bimodal positive electrode active material, the D50 particle diameter of the secondary particles may be 6㎛ to 10㎛.

D50 particle size means the diameter of particles having a cumulative volume of 50% by volume in the particle size distribution. Since the D50 particle diameter of the secondary particles satisfies the above numerical range, it is possible to expect the effect of improving the performance of the lithium secondary battery and improving the battery performance according to the particle size by preparing the positive active material in a bimodal form.

The secondary particles are metal oxide particles, and may include nickel, cobalt, manganese, and doping elements. Specifically, the metal oxide particles may include nickel, cobalt, manganese, and 60 mol% or more of nickel based on 100 mol% of the doping element.

Specifically, the positive active material according to an embodiment includes a compound represented by the following Chemical Formula 1.

[Formula 1]

Li _1+m Ni _1-wxyz Co _w Mn _x M1 _y M2 _z O _2-p X _p

In Formula 1, M1 and M2 are different from each other, and each of Al, Mg, Zr, Sn, Ca, Ge, Ti, Cr, Fe, Zn, Y, Ba, La, Ce, Sm, Gd, Yb, Sr, Cu And Ga is any one element selected from the group consisting of.

X is any one element selected from the group consisting of F, N, S, and P, and w, x, y, z, p and m are each 0.125<w<0.202, 0.153<x<0.225, 0=y= 0.1, 0=z=0.1, 0.34=w+x=0.36, 0=p=0.1, -0.1=m=0.2.

The cathode active material is manufactured by mixing a precursor and a lithium raw material and then firing the cathode active material. In this manufacturing process, lithium impurities such as Li ₂ CO ₃ and LiOH remain on the surface of the cathode active material.

Lithium impurities remaining on the surface of the positive electrode active material react with CO ₂ or H ₂ O in the air to form Li ₂ CO ₃ . Due to this, an initial irreversible capacity is formed, and there are problems such as hindering the movement of lithium ions on the surface of the positive electrode active material.

In order to solve such a problem, it is necessary to control the amount of lithium remaining on the surface of the positive electrode active material. Specifically, the amount of lithium remaining on the surface of the positive electrode active material may be suppressed by maintaining the nickel content above a certain value and increasing the manganese content.

In this embodiment, the content of nickel may be 0.66 or more. When the content of nickel is low, the expressed capacity of the secondary battery may be lowered. The manganese content may be greater than 0.153 and less than 0.225. When it is 0.153 or less, the content of Co, an expensive element, is relatively high, and structural stability may be affected. On the other hand, when it is 0.225 or more, since the content of cobalt and doping elements may be relatively reduced, electrochemical properties such as initial efficiency of the secondary battery may not be good.

The content of cobalt may be greater than 0.125 and less than 0.202. If it is 0.125 or less, electrochemical properties such as initial efficiency of the secondary battery may not be good. On the other hand, when it is 0.202 or more, it may be difficult to suppress the amount of lithium remaining on the surface of the positive electrode active material because the content of manganese may be relatively reduced.

That is, the amount of lithium remaining on the surface of the positive electrode active material can be suppressed by controlling the content of manganese and cobalt while the nickel content is maintained above a certain value, and excellent electrochemical properties can be expected.

M1 and M2 are heterogeneous elements doped into the positive electrode active material. Al, Mg, Zr, Sn, Ca, Ge, Ti, Cr, Fe, Zn, Y, Ba, La, Ce, Sm, Gd, Yb, Sr, Cu and Ga. Both may have a content of 0 or more and 0.1 or less.

X may be selected from the group consisting of F, N, S, and P as a coating element. m is a value satisfying -0.1=m=0.2.

More specifically, the positive electrode active material may include a compound represented by the following formula (2).

[Formula 2]

Li _1+m Ni _1-wx Co _w Mn _x O _2-p X _p

In Formula 2, X is any one element selected from the group consisting of F, N, S, and P, and w, x and m are each 0.351=w+x=0.354, 0=p=0.1, -0.1=m =0.2.

As the sum of the cobalt and manganese contents, w+x, is controlled in a numerical range of 0.351 or more and 0.354 or less, the nickel content may be 0.646 or more and 0.649 or less. When the content of nickel satisfies the above numerical range, it can be expected to secure electrochemical performance (capacity and lifespan characteristics) and structural stability.

Specifically, it may be 1.01=x/w=1.36. As mentioned above, the amount of lithium remaining on the surface of the positive electrode active material can be suppressed and excellent electrochemical properties can be expected by controlling the content of manganese and cobalt while maintaining the nickel content above a certain value. Therefore, the ratio of the manganese content to the cobalt content is adjusted.

Under the condition that the nickel content is 0.646 or more and 0.649 or less, when the manganese content to the cobalt content ratio is less than 1.01, the manganese content is not sufficient, so it may be difficult to suppress the amount of lithium remaining on the surface of the positive electrode active material. On the other hand, when it exceeds 1.36, the content of cobalt is relatively reduced, so it is difficult to expect excellent electrochemical properties of the secondary battery.

Next, in the bimodal positive active material of this embodiment, the content of Li ₂ CO ₃ remaining on the surface may be in the range of 1,500 ppm to 5,000 ppm or 2,000 ppm to 4,500 ppm. When the amount of lithium remaining on the surface of the positive electrode active material is less than 5000 ppm, lithium-containing impurities may decrease, thereby improving battery performance. On the other hand, when it exceeds 5,000 ppm, the electrochemical properties of the secondary battery may be deteriorated because problems such as generation of CO ₂ gas due to lithium-containing impurities on the surface of the positive electrode active material and the movement of lithium ions are hindered.

In another embodiment of the present invention, there is provided a lithium secondary battery comprising a positive electrode including the positive electrode active material according to an embodiment of the present invention described above, a negative electrode including a negative electrode active material, and an electrolyte positioned between the positive electrode and the negative electrode do.

The description related to the positive active material will be omitted because it is the same as the above-described exemplary embodiment of the present invention.

The positive active material layer may include a binder and a conductive material.

The binder serves to well adhere the positive active material particles to each other and also to adhere the positive active material to the current collector.

The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electronically conductive material may be used without causing a chemical change.

The negative electrode includes a current collector and a negative active material layer formed on the current collector, and the negative active material layer includes a negative electrode active material.

The negative active material includes a material capable of reversibly intercalating/deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

The material capable of reversibly intercalating/deintercalating the lithium ions is a carbon material, and any carbon-based negative active material generally used in lithium ion secondary batteries may be used, and a representative example thereof is crystalline carbon. , amorphous carbon or these may be used together.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn from the group consisting of Alloys of metals of choice may be used.

Examples of the material capable of doping and dedoping lithium include Si, SiO _x (0 < x < 2), Si-Y alloy (wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, An element selected from the group consisting of rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn-Y (wherein Y is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, a rare earth) an element selected from the group consisting of elements and combinations thereof, not Sn); and the like.

Examples of the transition metal oxide include vanadium oxide and lithium vanadium oxide. The negative active material layer also includes a binder, and may optionally further include a conductive material.

The binder serves to well adhere the negative active material particles to each other and also to adhere the negative active material to the current collector.

The conductive material is used to impart conductivity to the electrode, and in the configured battery, any electronically conductive material may be used without causing a chemical change.

As the current collector, one selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with conductive metal, and combinations thereof may be used.

The negative electrode and the positive electrode are prepared by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and applying the composition to a current collector. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted herein. The solvent may include, but is not limited to, N-methylpyrrolidone.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The lithium salt is dissolved in an organic solvent, serves as a source of lithium ions in the battery, enables basic lithium secondary battery operation, and promotes movement of lithium ions between the positive electrode and the negative electrode.

Depending on the type of lithium secondary battery, a separator may exist between the positive electrode and the negative electrode. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used. A polyethylene/polypropylene two-layer separator, a polyethylene/polypropylene/polyethylene three-layer separator, and polypropylene/polyethylene/poly It goes without saying that a mixed multilayer film such as a propylene three-layer separator or the like can be used.

Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries according to the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin-type, pouch-type, etc. according to the shape, According to the size, it can be divided into a bulk type and a thin film type. Since the structure and manufacturing method of these batteries are well known in the art, a detailed description thereof will be omitted.

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

Example 1

(1) Preparation of a cathode active material precursor

NiSO ₄ *6H ₂ O, CoSO ₄ *7H ₂ O, and MnSO ₄ *H ₂ O were measured using 64.6 mol% of Ni, 15 mol% of Co, and 20.4 mol of Mn as a target, and then dissolved in distilled water to prepare an aqueous metal salt solution.

A co-precipitation reaction facility consisting of one main reactor and one or more auxiliary reactors and a concentrator was used. In the co-precipitation reaction facility, when the reaction liquid input to the main reactor is full, the reactants are introduced into the auxiliary reactor, and the concentrated reaction liquid is circulated to the main reactor using the provided concentration equipment, that is, it is operated in a continuous circulation concentration method. .

The flow rate of the concentrate through the concentration facility is three times or more compared to the flow rate of the raw material fed into the main reactor, so that the reaction can be homogenized. One reactor with the same volume of the main reactor and the auxiliary reactor is used Compared to the case of circulating to the reactor after concentration, the number of precursor seeds can be increased more than twice, so the growth rate of the generated seeds can be controlled sufficiently slowly to produce high-strength, high-strength, single-particle precursors with high sphericity. can be obtained

The metal aqueous solution, ammonia, and caustic soda (NaOH) are introduced into the main reactor of the coprecipitation reaction facility to perform a coprecipitation reaction. The precipitate obtained according to the co-precipitation reaction was filtered with a filter press, washed with distilled water, and then residual moisture was removed using high-pressure fresh air. Next, the obtained product from which moisture was removed was dried at 150° C. using a fluidized bed dryer to prepare a cathode active material precursor.

As the precursor, a large particle diameter precursor having an average particle diameter of 9.5 μm and a small particle diameter precursor having an average particle diameter of 4.0 μm were separately prepared.

(2) Preparation of positive electrode active material

After mixing the precursor prepared in (1) with Li ₂ CO ₃ , 4.0 kg of the mixed precursor was filled in a saggar made of a mullite material.

Next, the filling material was heated to 880° C. in an oxygen atmosphere (temperature increase rate of 3.0° C./min), maintained at 800 to 880° C. for 15 hours, and cooled for 5 hours to prepare a positive electrode active material with a large particle diameter and a small particle diameter, respectively.

Large particle diameter and small particle diameter positive electrode active material is uniformly mixed in a weight ratio of 8: 2 (large particle diameter: small particle diameter), and after additional mixing of the coating material, it is maintained for 12 hours at 400°C heat treatment condition, heat treated for coating, and sintered The material was pulverized and classified to prepare a positive active material of Example 1 in a bi-modal form.

At this time, the coating was carried out using boric acid (H ₃ BO ₃ ) to prepare a cathode active material having a coating layer by heat-treating the mixture after mixing so that the content of element B was 1,000 ppm.

(3) Preparation of lithium secondary battery

The cathode active material, conductive material (Denka black), and polyvinylidene fluoride (PVDF) binder prepared in (2) are mixed in a weight ratio of 94:3:3, and the mixture is mixed with N so that the solid content is about 50% by weight. -Methyl-2 pyrrolidone was added to a solvent to prepare a cathode active material slurry.

The slurry was evenly coated on aluminum foil, pressed in a roll press, and vacuum dried in a vacuum oven at 150° C. for 12 hours to prepare a positive electrode.

A coin-type half-coin cell was prepared in a conventional manner using lithium metal as a counter electrode, an electrolyte, and a polypropylene separator.

The electrolyte was used by dissolving 1 mol of LiPF ₆ in a mixed solvent of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 1:2.

Example 2

A cathode active material of Example 2 was prepared in the same manner as in Example 1, except that the raw material content of each element was adjusted so that the ratios of nickel, cobalt, and manganese were as shown in Table 1 below.

Comparative Examples 1 to 4

Comparative Examples 1 to 1 in the same manner as in Example 1, except that the ratio of nickel, cobalt, and manganese was adjusted as shown in Table 1 below, and the raw material content of each element was adjusted, and a conventional batch reactor was used during the coprecipitation reaction. A positive active material of Comparative Example 4 was prepared.

Evaluation Example 1 - Particle Strength of Precursor and Active Material

20 each of the large particle precursors and the large particle active materials prepared according to Examples 1 to 2 and Comparative Examples 1 to 4 were selected, and the maximum and minimum values were measured using a particle strength measuring device (MCT-W500 Micro particle compression test of Shimadzu Corporation). And the particle strength measurement results for 15 particles from which the noise has been removed are shown in Table 1 below.

The particle strengths in Table 1 below are average values for 15 particles.

The particle strength is a value obtained by dividing the force applied to the particle by the cross-sectional area of the particle, and is calculated by the following Equation 1, and has a unit of MPa.

[Equation 1]

St = 2.8 P/(πd ² )

In this case, St is the particle strength (tensile strength, MPa), P is the applied pressure (test force, N), and d is the diameter of the particle (mm).

division Precursor Preparation NiCoMn
(Mol%) Large particle size precursor particle strength (Mpa) Large particle size active material particle strength (Mpa) Example 1 Continuous Circulation Concentration 64.6 15 20.4 82 142 Comparative Example 1 general policy 64.6 15 20.4 60 115 Comparative Example 2 general policy 65 12.5 22.5 54 120 Example 2 Continuous Circulation Concentration 64.9 17.4 17.7 85 140 Comparative Example 3 general policy 64.5 20.2 15.3 56 118 Comparative Example 4 general policy 64.9 17.4 17.7 62 120

Referring to Table 1, the particle strength of the large particle diameter precursor and the large particle diameter cathode active material of Examples 1 and 2 using the continuous circulation concentration method is the large particle diameter precursor and the large particle diameter prepared by Comparative Examples 1 to 4 using a common coprecipitation reactor It can be seen that the particle strength is higher than that of the positive electrode active material.

Evaluation Example 2 - Measurement of particle size retention of large particle diameter, small particle diameter, and bimodal positive active material

Large particle diameter, small particle diameter, and particle diameter retention of the bimodal positive electrode active material prepared according to Examples 1 to 2 and Comparative Examples 1 to 4 were measured.

Pressed density was measured using Carver_4350.

After 3 g of the positive electrode active material was put into the cylindrical mold, the large particle diameter, the small particle diameter and the bimodal positive electrode active material were respectively pressurized at a pressure of 1.75 to 2.0 tons. After the pellets were prepared by pressurization, the particle size distribution before/after pressurization was measured for each large particle diameter, small particle diameter, and bimodal positive electrode active material.

The results are shown in Tables 2 to 4 below.

pressure (tons) D5 particle size
retention rate D10 particle size
retention rate Example 1 0 (before press) 6.4 100% 7 100% 2 5.7 90.10% 6.3 90.40% Comparative Example 1 0 (before press) 6.3 100% 6.9 100% 2 5.3 83.60% 6.1 87.80% Comparative Example 2 0 (before press) 6.4 100% 7.1 100% 2 5.3 82.80% 6.2 87.30% Example 2 0 (before press) 6.8 100% 7.2 100% 2 5.9 86.80% 6.6 91.70% Comparative Example 3 0 (before press) 6.3 100% 7 100% 2 5.1 81.00% 6 85.70% Comparative Example 4 0 (before press) 6.2 100% 6.9 100% 2 5.1 82.30% 6 87.00%

Referring to Table 2, in the case of the large particle diameter active materials prepared in Examples 1 and 2, the particle size retention rates before and after pressing in the cylindrical mold were 86.8% to 90.1% based on D5, and 90.4 to 91.7% based on D10. On the other hand, in the case of the large particle diameter active materials prepared in Comparative Examples 1 to 3, the particle size retention rates before and after pressing in the cylindrical mold were 81.0 to 83.6% based on D5 and 85.7% to 87.8% based on D10.

pressure (tons) D50(㎛) Particle size retention rate (%) Example 1
(small diameter) 0 (before press) 4.70 100 1.75 3.35 71.2 Comparative Example 1
(small diameter) 0 (before press) 4.50 100 1.75 3.06 68.0 Comparative Example 2
(small diameter) 0 (before press) 4.42 100 1.75 2.92 66.1 Example 2
(small diameter) 0 (before press) 4.63 100 1.75 3.27 70.6% Comparative Example 3
(small diameter) 0 (before press) 4.35 100% 1.75 2.89 66.4% Comparative Example 4
(small diameter) 0 (before press) 4.73 100% 1.75 3.18 67.2%

Referring to Table 3, the small particle size active material prepared according to Examples 1 and 2 had a particle size retention ratio of 70.6% to 71.2% based on D50 before/after pressing in a cylindrical mold.

On the other hand, the small particle diameter active material prepared according to Comparative Examples 1 to 3 had a particle diameter retention ratio of 66.1% to 68.0% based on D50 before/after pressing in a cylindrical mold,

pressure (tons) D5 (μm) particle size D10 (μm) particle size Retention (%) Retention (%) Example 1
(bimodal) 0 (before press) 3.1 100 3.9 100 1.75 2 63.6 2.7 69.2 Comparative Example 1
(bimodal) 0 (before press) 3.1 100 4 100 1.75 1.7 55.5 2.5 62.3 Comparative Example 2
(bimodal) 0 (before press) 2.9 100 3.7 100 1.75 1.7 58.60% 2.2 59.50% Example 2
(bimodal) 0 (before press) 3.1 100% 3.6 100% 1.75 1.9 61.30% 2.4 66.70% Comparative Example 3
(bimodal) 0 (before press) 3.3 100% 4 100% 1.75 1.9 57.60% 2.4 60.00% Comparative Example 4
(bimodal) 0 (before press) 3.2 100% 3.9 100% 1.75 1.8 56.30% 2.4 61.50%

Referring to Table 4, in the case of the bimodal positive active material prepared according to Examples 1 and 2, the particle size retention before and after pressing in the cylindrical mold was 61.3% to 63.6% based on D5, and 66.7% to 69.2% based on D10. On the other hand, in the case of the bimodal positive electrode active material prepared according to Comparative Examples 1 to 4, the particle size retention before and after pressing in the cylindrical mold was 55.5% to 58.6% based on D5, and 59.5% to 62.3% based on D10.

Therefore, referring to Tables 2 to 4, the large particle diameter, small particle diameter and bimodal active material of Examples prepared by the continuous circulation concentration co-precipitation method had a higher overall particle size retention before and after pressurization than the large particle diameter, small particle diameter, and bimodal active material of Comparative Examples can check that

This is considered to be because the precursor prepared by the continuous circulation concentration co-precipitation method has high sphericity and high strength characteristics.

Evaluation Example 3 - Residual Lithium Amount

The amount of Li ₂ CO ₃ remaining on the surface of the positive electrode active material of Examples and Comparative Examples is recorded in Table 5 below.

Residual lithium measurement method is as follows. Put magnetic and ultrapure water 100ml into a beaker (100ml, glass). Put the weighed sample (5 g) in a beaker and cover with parafilm to prevent foreign matter from entering. Set the stirring speed (650 rpm), time (10 min) and stir. The sample after stirring is filtered (Glass Micro Fiber Filter). When the filtration is complete, the eluted solution is placed in a Disposable Beaker, and titration is performed with 0.1N HCl solution (Mettler Toledo T70).

division Residual lithium (based on Li ₂ CO ₃ )
(ppm) Example 1 2,864 Comparative Example 1 2,834 Comparative Example 2 2,572 Example 2 3,546 Comparative Example 3 4,263 Comparative Example 4 3,621

Referring to Table 5, it can be seen that the amount of lithium remaining on the surface of the finally obtained positive electrode active material decreases as the nickel content is the same, but the manganese content is increased.

However, when the nickel content is the same, as the manganese content increases, the cobalt content decreases, so the effect will be investigated in Evaluation Example 4 below.

Evaluation Example 4 - Coin Cell Initial Resistance and Efficiency Evaluation

The batteries to which the positive active materials of Examples and Comparative Examples were applied were driven under the following conditions, and 0.1 C capacity and initial efficiency were recorded in Table 6.

Charge: 1.0C, CC/CV 4.25V, 1/20C cut-off

Discharge: 1.0C, CC, 3.0V cut-off

division 0.1 C capacity (mAh/g) Initial Efficiency (%) Example 1 186.5 89.9 Comparative Example 1 187.8 90.1 Comparative Example 2 182.3 88.6 Example 2 188 89.3 Comparative Example 3 185.9 88.6 Comparative Example 4 187.7 89.6

Referring to Table 6, in the case of Comparative Example 3 with a high amount of residual lithium on the surface of the positive electrode active material, it can be seen that the initial capacity and efficiency are lower than those of Examples 1 and 2.

On the other hand, in the case of Comparative Example 2, it can be seen that the amount of residual lithium on the surface is relatively low, but the electrochemical properties of the battery are not good as the cobalt content is low and the manganese content is relatively high.

Evaluation Example 5 - Room temperature life evaluation

A battery to which each active material (sintering temperature: 880°C) was applied at room temperature (25°C) was driven under the following conditions, and the capacity retention ratio after 25 cycles of operation compared to the initial capacity was recorded in Table 7.

Charge: 1.0C, CC/CV 4.3V, 1/20C cut-off

Discharge: 1.0C, CC, 3.0V cut-off

division Example 1 Comparative Example 1 Comparative Example 2 Example 2 Comparative Example 3 Comparative Example 4 880℃ 25/1 cyc 97.6% 97.3% 98.2% 97.2% 96.4% 96.8%

Referring to Table 7, it can be seen that the performance of Example 1 is the best. This is considered to be due to the amount of residual lithium and manganese ?t.

Evaluation Example 6 - High Temperature Life Evaluation

At 45° C., the batteries to which each active material (calcination temperature: 880° C.) was applied were driven under the following conditions, and the capacity retention ratio after 25 cycles compared to the initial capacity was recorded in Table 8.

Charge: 1.0C, CC/CV 4.3V, 1/20C cut-off

Discharge: 1.0C, CC, 3.0V cut-off

division Example 1 Comparative Example 1 Comparative Example 2 Example 2 Comparative Example 3 Comparative Example 4 880℃ 25/1 cyc 98.4% 98.2% 98.6% 98.0% 97.1% 97.5%

Referring to Table 8, it can be seen that the performance according to Example 1 is the best among Examples. Likewise, this is due to the amount of residual lithium and manganese content.

Evaluation Example 7 - Monocell High Temperature Life Evaluation

After driving the mono cell under the conditions of 3.0V ~ 4.25V, 1C(CC-CV, 0.05C)/1C(CC)(rest 10min) @ 45℃, 400cycle, high-temperature capacity retention rate and resistance increase rate were recorded in Table 9 .

Example 1 Comparative Example 1 Comparative Example 2 Example 2 Comparative Example 3 Comparative Example 4 Capacity retention rate (%) 90.2 86 85.2 89.0 84.7 85.4 Resistance increase rate (%) 124 165 172 138 175 168

Referring to Table 9, in the case of Examples 1 and 2 using the high-strength precursor having a high sphericity prepared by the continuous circulation concentration co-precipitation method, compared to Comparative Examples 1 to 4, the capacity retention rate and low resistance increase rate were shown. can be checked In particular, in Example 1 and Comparative Example 1, Example 2, and Comparative Example 4 having the same composition, the effect of applying the continuous circulation concentration co-precipitation method can be confirmed.

Evaluation Example 8 - Coin Cell High Temperature Storage Evaluation

The capacity retention rate and resistance increase rate were recorded in Table 10 by driving a mono cell under storage conditions of 4 weeks at room temperature SOC100% setting (0.33C CCCV charging) @ 60°C.

Example 1 Comparative Example 1 Comparative Example 2 Example 2 Comparative Example 3 Comparative Example 4 Capacity retention rate (%) 95 91 89.2 94.5 88.4 90.5 Resistance increase rate (%) 149 176 178 155 175 172

Referring to Table 10, as can be seen from the 60 degree high temperature storage results of Examples 1 to 2 and Comparative Examples 1 to 4, in the case of Examples using high-strength precursors having high sphericity prepared by continuous circulation concentration co-precipitation method, compared to Comparative Examples Excellent high-temperature storage characteristics can be confirmed.

In particular, in Example 1 and Comparative Example 1, Example 2, and Comparative Example 4 having the same composition, the effect of applying the continuous circulation concentration co-precipitation method can be confirmed.

From the results of Tables 9 and 10, when the positive electrode active material obtained from a high-strength precursor with high sphericity was pressed (surface pressure) in a cylindrical mold, as well as when applied to an actual electrode (linear pressure), slip between particles due to high sphericity was It can be seen that particle deformation during pressurization is minimized compared to the cathode active material obtained by the existing precursor method in terms of particle deformation relief due to high strength characteristics and durability under pressure due to high strength characteristics.

The present invention is not limited to the above embodiments, but can be manufactured in various different forms, and those of ordinary skill in the art to which the present invention pertains can take other specific forms without changing the technical spirit or essential features of the present invention. It will be understood that it can be implemented as Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (11)

a large particle diameter positive electrode active material having an average particle diameter in the range of 7 μm to 11 μm; and
Including; a small particle diameter positive electrode active material having an average particle diameter in the range of 3 μm to 5 μm;
When the bimodal positive active material including the large-diameter positive active material and the small-diameter positive active material is pressurized to 1.75 tons using a pressurizing device, the particle size retention before/after pressurization is 60% or more based on D5. According to claim 1,
The bimodal positive electrode active material,
When pressurized to 1.75 tons using pressurization equipment, the positive electrode active material has a particle size retention rate of 65% or more before/after pressurization based on D10. According to claim 1,
When the large particle diameter positive active material is pressurized to 2.0 tons using a pressurizing device, the positive electrode active material has a particle size retention rate of 85% or more based on D5 before/after pressurization. According to claim 1,
When the large particle diameter positive active material is pressurized to 2.0 tons using a pressurizing device, the positive electrode active material has a particle size retention rate of 89% or more based on D10 before/after pressurization. According to claim 1,
When the small particle diameter positive active material is pressurized to 1.75 tons using a pressurizing device, the particle size retention ratio before/after pressing is 70% or more based on D50. The method of claim 1,
The particle strength of the large-diameter positive electrode active material is 140Mpa or more. According to claim 1,
The mixing ratio of the large particle diameter positive electrode active material and the small particle diameter positive electrode active material,
A positive active material in the range of 9: 1 to 6: 4 by weight. According to claim 1,
The bimodal positive electrode active material is a positive electrode active material in the form of secondary particles including a plurality of primary particles. 9. The method of claim 8,
The average particle diameter of the primary particles is in the range of 0.1 μm to 1 μm, positive active material. According to claim 1,
The positive active material includes a compound represented by the following formula (1).
[Formula 1]
Li _1+m Ni _1-wxyz Co _w Mn _x M1 _y M2 _z O _2-p X _p
(In Formula 1, M1 and M2 are different from each other, and Al, Mg, Zr, Sn, Ca, Ge, Ti, Cr, Fe, Zn, Y, Ba, La, Ce, Sm, Gd, Yb, Sr, Any one element selected from the group consisting of Cu and Ga,
X is any one element selected from the group consisting of F, N, S, and P, and w, x, y, z, p and m are each 0.125<w<0.202, 0.153<x<0.225, 0=y= 0.1, 0=z=0.1, 0.34=w+x=0.36, 0=p=0.1, -0.1=m=0.2) According to claim 1,
The content of Li ₂ CO ₃ remaining on the surface of the positive active material is in the range of 1,500 ppm to 5,000 pm.