WO2021145493A1

WO2021145493A1 - Precursor particle for producing positive electrode active material comprising coating layer

Info

Publication number: WO2021145493A1
Application number: PCT/KR2020/000899
Authority: WO
Inventors: 진주성; 장성균; 박선홍; 김도형
Original assignee: 주식회사 엘 앤 에프
Priority date: 2020-01-17
Filing date: 2020-01-17
Publication date: 2021-07-22

Abstract

The present invention provides a precursor particle for producing a positive electrode active material, comprising: a precursor core comprising at least one transition metal; and a coating layer added to the outer surface of the precursor core, and comprising at least one element selected from among an alkali metal, an alkaline earth metal, a metalloid and a post-transition metal of groups 13 to 15, and a nonmetal of groups 14 to 16.

Description

Precursor particles for producing a cathode active material containing a coating layer

The present invention relates to precursor particles for producing a cathode active material, and more particularly, a cathode active material comprising a precursor core including one or more transition metals, and a coating layer added to the outer surface of the precursor core and having a specific composition It relates to precursor particles for

Globally, the secondary battery market is expected to continue to expand due to the demand for new and renewable energy in accordance with fuel economy regulation cooperation. In the 1990s, not only small mobile devices but also medium and large secondary batteries such as HEVs, PHEVs, EVs, and ESSs continued to develop, and there is a need for secondary battery technology that satisfies high capacity and high voltage. Currently, in order to satisfy these conditions, the development of a high nickel-based NCM with a high Ni content is in progress as a positive electrode active material.

However, as the content of Ni in the positive electrode active material increases, a problem due to instability occurs. During firing, Li does not form a proper layered structure and remains on the surface due to Ni, and this residual lithium causes a side reaction with carbon dioxide gas and electrolyte, resulting in a swelling phenomenon in which the battery cell swells. That is, as the Ni content increases, the residual lithium also increases during the manufacturing process.

In order to improve this phenomenon, Li must be uniformly diffused into the transition metal precursor particles during firing to form a stable layered structure, but the conventional precursor structure has limitations.

In general, in order to sinter into a cathode active material, NCM(OH) ₂ or NCM(OOH) _{, which is a particle-shaped transition metal precursor, and Li 2} CO ₃ , LiOH, etc., which are lithium precursors, are mixed using a Kawata mixer, zet mill, etc. mixing equipment. Mix. However, there is a problem in that particles are broken or cracked due to physical damage caused by mixing blades such as mixers and collisions between particles.

In addition, there is a problem in that the mixing uniformity of the transition metal precursor and the Li precursor is low, and the density is low because the Li precursor and the transition metal precursor are in a simple mixed state rather than in close contact. the current situation.

An object of the present invention is to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

After repeated in-depth research and various experiments, the inventors of the present application have developed a novel precursor particle that can be used as a main raw material for a cathode active material for a secondary battery, and these precursor particles include a precursor core and a coating layer of a specific composition. It is possible to synthesize the cathode active material by only firing itself or to coat or dope the material in the cathode active material without an additional process, and it is possible to provide a cathode active material with excellent properties as the diffusivity and reactivity are remarkably improved, and alkali In the case of forming Li among the metals on the surface of the precursor core, it was confirmed that residual lithium in the positive electrode active material can be drastically reduced, thereby essentially preventing the swelling phenomenon in the positive electrode active material having a high Ni content, and the present invention came to completion.

First, the meaning of the term 'precursor' will be described to help a clear understanding of the present invention.

In general, in the art, a transition metal material and an alkali metal material used to manufacture a positive electrode active material are each expressed as a 'precursor', and in the case of an alkali metal material, it is also expressed as a 'raw material' rather than a precursor.

These transition metal precursors and alkali metal precursors contain both the meaning of each 'metal particle' and the meaning of 'a powder (powder) of a large number of particles', and in the art, both particles and powder are commonly referred to as precursors. have. Hereinafter, in order to avoid confusion of terms, 'particle' and 'powder' are separately expressed.

As described later, the precursor powder according to the present invention means a collection of a plurality of precursor particles, but since the precursor particles are prepared in a large amount of powder rather than prepared one by one, alkali metals that are not included in the coating layer of the precursor particles, etc. Silver may be present in the precursor powder as a separate substance, or more precisely, between precursor particles.

Precursor particles for producing a positive active material according to the present invention,

A precursor core containing one or more transition metals; and

a coating layer added to the outer surface of the precursor core and comprising at least one selected from alkali metals, alkaline earth metals, post-transition metals and metalloids in Groups 13 to 15, and non-metal elements in Groups 14 to 16;

It is characterized in that it contains

Conventionally, the positive electrode active material is synthesized by mixing and firing the transition metal precursor particles constituting the positive electrode active material and precursor particles such as lithium, or the positive electrode active material is coated or doped with a specific material. However, the precursor particles according to the present invention are each a precursor of a specific composition Since it contains a core and a coating layer, it is possible to synthesize a cathode active material just by firing itself or to coat or dope a material without an additional process, and it is possible to provide a cathode material with excellent properties by remarkably improving diffusivity and reactivity. can

In particular, when Li among alkali metals is included as a coating layer on the surface of the precursor core, residual lithium in the positive electrode active material can be dramatically reduced, which essentially prevents the swelling of the battery cell in the positive electrode active material with a high Ni content. can do.

Specifically, in the prior art, lithium precursor particles and transition metal precursor particles prepared for each were simply mixed, and when calcined at high temperature to make a positive electrode active material, the lithium precursor particles were melted and diffused into the transition metal precursor particles to form a positive electrode active material.

In this conventional method, since the lithium precursor particles and the transition metal precursor particles exist separately, the diffusion distance of lithium into the transition metal precursor particles is long and the probability of mutual contact is not high. Residual lithium increased because it did not diffuse into the transition metal precursor and remained on the surface.

On the other hand, since the precursor particles according to the present invention include a precursor core of a specific composition and a coating layer of a specific composition added to the outer surface thereof, this problem can be solved, and in particular, when a secondary battery having a high Ni content is applied, Ni It is possible to suppress the increase of residual lithium in spite of an increase in the content.

In one specific example, the precursor core may be a hydroxide-based material having the composition of Formula 1 below, and when M contains two or more transition metals, it may be synthesized by, for example, a co-precipitation method.

(1-xy)M(OH) ₂ *xMOOH*yM(OH _1-z ) ₂ (1)

In the above formula,

0≤x≤1, 0≤y≤1, 0≤(1-x-y)≤1, 0<z<0.5;

M contains one or more transition metals that are stable in the tetracoordinate or hexacoordinate.

When M contains two or more transition metals, for example, one or more elements selected from elements belonging to Groups 5 (VB) to 11 (Group VIIIB) on the periodic table and nickel (Ni) are included. can do. In this case, the content of Ni may be preferably 40 mol% or more, more preferably 50 mol% or more, and particularly preferably 60 mol% or more.

Specific examples of the elements belonging to Group 5 (Group VB) to Group 11 (Group VIIIB) include Ti, Sc, V, Cr, Mn, Fe, Co, Y, Cu, Zr, Nb, Mo, Tc, Ru, Rh , Ag, Pd, etc., but are not limited thereto, and in one specific example, M is Ti, Sc, V, Cr, Mn, Fe, Co, Y, Cu, Zr, Nb, Mo, Tc, It may include Ni and at least one element selected from the group consisting of Ru, Rh, Ag and Pd.

Preferably, M may further include one or more of Co and Mn in addition to Ni, for example, may be formed of a combination of Ni and Co and Mn.

In Chemical Formula 1, the site of oxygen or hydrogen may be defective as is generally known, and in the case of an anion, it may be equivalently partially substituted with an anion such as _{S, F, PO 4} , SO _{4 .}

In one specific example, in the coating layer, the alkali metal is at least one selected from the group consisting of Li, Na, K, Rb, Cs and Fr, and the alkaline earth metal is Be, Mg, Ca, Sr, Ba and Ra. At least one selected from the group consisting of, the post-transition metals and metalloids in Groups 13 to 15 are Al, Ga, In, Sn, Tl, Pb, Bi, Po, B, Si, Ge, As, Sb, It is at least one selected from the group consisting of Te and At, and the non-metal element in Groups 14 to 16 may be at least one selected from the group consisting of C, P, S, and Se.

The coating layer may preferably include Li. At this time, when Ni as a transition metal is contained in a high content in the precursor core, the amount of residual lithium in the positive electrode active material manufactured through firing can be significantly reduced.

As another example, when the coating layer contains, for example, B in addition to Li, when the precursor particles including such a coating layer are fired, a B-doped anode based on Li and a transition metal without going through a separate additional firing process An active material can be prepared.

In one specific example, the coating layer may include a material having a composition of Formula 2 below.

(1-vw)A ₂ CO ₃ *vAOH*wA ₂ O (2)

In the above formula,

0≤v≤1, 0≤w≤1, 0≤(1-v-w)≤1;

A is at least one alkali metal and/or alkaline earth metal.

The coating layer may include, for example, Li ₂ CO ₃ , LiOH, NaOH, KOH, and the like.

In one specific example, the coating layer may be configured to include two or more different elements.

In the above formula (2), the site of oxygen or hydrogen may be defective as is generally known as in the description of the formula (1), and when A is, for example, an alkaline earth metal, it may have a molar ratio of 1/2 compared to the alkali metal. have.

In the precursor particles of the present invention, A/M (molar ratio), which is the ratio of the content of the transition metal (M) in the precursor core and the content of the element (A) included in the coating layer, is, for example, 0.6 to 1.5, preferably 0.8 to 1.4, more Preferably it may be in the range of 0.9 to 1.3.

Element (A) included in the coating layer in the precursor particles of the present invention is not included in the precursor core, which can be confirmed from the results of FIGS. 4 and 5 .

That is, referring to these drawings, while potassium (K) does not exist in the NMC precursor (site '1'), which is the precursor core, site '2' and site '3' that are the outer surface of the NMC precursor corresponding to the coating layer. It can be seen that potassium is present in For reference, carbon is a separately added coating material for the ease of EDS detection.

The precursor particles according to the present invention may be in the form of primary particles or secondary particles, preferably secondary particles. The secondary particle (granular) is formed by agglomeration of fine-sized primary particles to form a relatively large-sized shape (a primary particle is expressed as a particle meaning one particle, and a secondary particle is 1 It is expressed as granular, meaning the granular state in which tea particles are aggregated).

The size of the primary particles may be, for example, in the range of 0.01 μm to 10 μm, and the size of the secondary particles may be in the range of 2 μm to 100 μm under conditions larger than the primary particles, but is not particularly limited.

The precursor particles according to the present invention can control the firing temperature, time, etc. to variously control the particle size (particle diameter), and it is also possible to prepare a precursor powder to be described later by mixing two or more types of novel precursor particles having different particle diameters. Do. In this case, the particle size can be confirmed by measuring a general PSD (Particle Size Distribution), and it is also possible to measure the long axis and the short axis of the primary particle or secondary particle through an SEM image, etc.

The precursor particles according to the present invention can be prepared by various methods. For example, a basic-based washing and filtration process to obtain a precipitate containing one or more, preferably two or more transition metal elements by co-precipitation, and to remove acidic components of the transition metal salt used for co-precipitation as a post-process A method of adding a coating layer element-containing compound to the result of the subsequent drying process or a method of adding a coating layer element-containing compound during aggregation of the primary particles obtained by the co-precipitation process into secondary particles may be mentioned. It is not limited.

In addition, the present invention provides a precursor powder comprising the aforementioned precursor particles.

The precursor powder according to the present invention may be calcined by itself to prepare a cathode active material, or a cathode active material may be prepared by adding a compound including one or a portion of the elements forming the coating layer and then calcining.

The calcination may be carried out in an oxygen-containing atmosphere such as air, for example, at a temperature range of 750 to 1000 ℃, specifically 760 to 950 ℃, for example, 10 to 30 hours, specifically 16 to 25 hours. have.

The present invention also provides a cathode active material, characterized in that produced by firing the precursor powder, and a secondary battery comprising the cathode active material.

Since the configuration and manufacturing method of the secondary battery are known in the art, a detailed description thereof will be omitted herein.

As described above, the precursor particles according to the present invention are capable of synthesizing a cathode active material only by sintering themselves or coating or doping of a material without an additional process, and a positive electrode with excellent properties due to remarkably improved diffusivity and reactivity It is possible to provide an active material, and depending on the composition, it is possible to dramatically reduce residual lithium in the positive electrode active material, so that it is possible to essentially prevent the swelling phenomenon in the positive electrode active material having a high Ni content.

1 is an SEM photograph of precursor particles prepared in Example 1 of the present invention;

2 and 3 are SEM photographs of precursor particles prepared in Comparative Example 1;

4 and 5 are results of mapping analysis based on EDS in Experimental Example 2 of the present invention.

Hereinafter, the present invention will be further described with reference to the drawings according to embodiments of the present invention, but the scope of the present invention is not limited thereto.

[Example 1]

Sulfates of nickel, cobalt, and manganese were dissolved in a ratio of 5:2:3 (molar ratio) to make a solution, and then a co-precipitation reaction was performed to synthesize a precursor core having a composition of 5:2:3. _{Li 2} CO ₃ as a Li compound was dissolved in water from which impurities were removed to prepare a high concentration solution of 1M or more. The synthesized precursor core was washed using a circulating filtration device, and after washing and filtration, it was mixed with a high concentration Li solution and mixed and stirred so that the molar ratio of Li and metal was 1.03.

Then, moisture was removed through drying in a drying oven at 120° C. for 12 hours to prepare lithium-coated precursor particles.

The precursor particles prepared above were calcined at 940° C. while flowing air for 16 hours to prepare a cathode active material of _{Li[Ni 0.50} Co _0.20 Mn _0.30 ]O _{2 .}

[Comparative Example 1]

The Ni:Co:Mn ratio is 5:2:3, synthesized by co-precipitation, washed through a circulating filtration device, and then dried in an oven at 120°C for 12 hours to remove moisture to prepare precursor particles did.

_{Put the prepared precursor particles in a mixer, mix with Li 2} CO ₃ as a Li compound so that the molar ratio of Li and Metal becomes 1.03, and then bake at 940° C. while flowing air for 16 hours, and then Li[Ni _0.5 Co _0.2 Mn _0.3 A positive active material of ]O _{2 was prepared.}

[Example 2]

A precursor core having a composition of 8:1:1 was synthesized by dissolving sulfate salts of nickel, cobalt, and manganese in a ratio of 8:1:1 to make a solution, and then performing a coprecipitation reaction. LiOH as a Li compound was dissolved in water from which impurities were removed to prepare a high concentration solution of 1 M or more. The synthesized precursor core was washed using a circulating filtration device, and after washing and filtration, it was mixed with a high concentration Li solution and mixed and stirred so that the molar ratio of Li and metal was 1.03.

The precursor particles prepared above were calcined at 800° C. while flowing air for 24 hours to prepare a cathode active material of _{Li[Ni 0.80} Co _0.10 Mn _0.10 ]O _{2 .}

[Comparative Example 2]

Precursor particles are prepared by removing moisture by drying in an oven at 120° C. for 12 hours after washing through a circulation filtration device along with synthesis by co-precipitation with a composition in which the Ni:Co:Mn ratio is 8:1:1. did.

Put the prepared precursor particles in a mixer, mix them with LiOH as a Li compound so that the molar ratio of Li and Metal becomes 1.03, and then bake at 800 ° C. while flowing air for 24 hours, to obtain Li[Ni _0.8 Co _0.1 Mn _0.1 ]O ₂ A positive electrode active material was prepared.

[Example 3]

A precursor core having a composition of 9:0.5:0.5 was synthesized by dissolving sulfate salts of nickel, cobalt, and manganese in a ratio of 9:0.5:0.5 to make a solution, and then performing a co-precipitation reaction. LiOH as a Li compound was dissolved in water from which impurities were removed to prepare a high concentration solution of 1 M or more. The prepared precursor core was washed using a circulating filtration device, and after washing and filtration, it was mixed with a high concentration Li solution and mixed and stirred so that the molar ratio of Li and metal was 1.03.

The precursor particles prepared above were sintered at 780° C. while flowing air for 24 hours to prepare a cathode active material of _{Li[Ni 0.90} Co _0.05 Mn _0.05 ]O _{2 .}

[Comparative Example 3]

The Ni:Co:Mn ratio is 9:0.5:0.5, which is synthesized by co-precipitation reaction, washed through a circulating filtration device, and then dried in an oven at 120°C for 12 hours to remove moisture to prepare precursor particles did.

Put the prepared precursor particles in a mixer, mix with LiOH as a Li compound so that the molar ratio of Li and Metal becomes 1.03, and then sinter at 780 ° C. while flowing air for 24 hours to obtain Li[Ni _0.9 Co _0.05 Mn _0.05 ]O ₂ A positive electrode active material was prepared.

[Experimental Example 1]

1 to 3 are SEM photographs comparing the state of the precursor particles prepared in Example 1 before firing and the precursor particles prepared in Comparative Example 1 before firing.

As shown in FIG. 1, it can be seen that the precursor particles according to the present invention have a smooth surface, which can be understood as a result of uniformly applying a coating layer on the surface of the precursor core.

On the other hand, as shown in FIGS. 2 and 3 , the precursor particles of Comparative Example have a rough surface, and in some cases, the precursor particles are destroyed in the process of mixing with the Li compound (see FIG. 2 ), and in some cases, the Li compound is the precursor particles even after mixing. It can be seen that it is not uniformly applied to the surface of the , and is only partially attached to the surface of the precursor particles (see FIG. 3 ).

[Experimental Example 2]

4 and 5 show the EDS component analysis results of the precursor particles prepared in the same manner as in Example 1, but by applying a potassium compound (KCl) instead of a lithium compound.

4 and 5, it can be seen that potassium is not present in the precursor core, but is present only in the coating layer, which is the outer surface of the precursor core.

[Experimental Example 3]

In order to analyze the residual lithium in the positive electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3, respectively, a potentiostatic neutralization titration method using an HCl solution was used. Using the prepared positive electrode active material, Li ₂ CO ₃ and LiOH, which are compounds containing residual lithium, were respectively measured, and the total amount of Li alone (TTL, Total Lithium) was calculated as follows and shown in Table 1.

[formula]

Total Lithium (TTL) = Li ₂ CO ₃ measured value (%) * 2Li/Li ₂ CO ₃ + LiOH measured value (%) * Li/LiOH

→ Li ₂ CO ₃ measured value (%) * 0.188 + LiOH measured value (%) * 0.29

[Table 1]

As shown in Table 1, in the positive electrode active materials of the same transition metal composition, it can be seen that the positive electrode active materials of Examples 1 to 3 according to the present invention have low residual lithium compared to the positive electrode active materials of Comparative Examples 1 to 3 . This reduction in residual lithium can prevent swelling of the battery cell in the positive electrode active material having a high Ni content.

Those of ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Claims

A precursor core containing one or more transition metals; and

Precursor particles for producing a cathode active material, characterized in that it contains a.

[2] The precursor particle of claim 1, wherein the precursor core is a hydroxide-based material having a composition of Formula 1

(1-xy)M(OH) ₂ *xMOOH*yM(OH _1-z ) ₂ (1)

In the above formula,

0≤x≤1, 0≤y≤1, 0≤(1-x-y)≤1, 0<z<0.5;

3. The method of claim 2, wherein M includes nickel (Ni) and at least one element selected from elements belonging to Groups 5 (VB) to 11 (Group VIIIB) on the periodic table, and the Ni content is 40 mol% Precursor particles for producing a positive electrode active material, characterized in that the above.

According to claim 2, wherein M is one or more selected from the group consisting of Ti, Sc, V, Cr, Mn, Fe, Co, Y, Cu, Zr, Nb, Mo, Tc, Ru, Rh, Ag and Pd Precursor particles for producing a cathode active material, characterized in that it contains an element and Ni.

The precursor particle according to claim 3, wherein M further comprises at least one of Co and Mn.

The method of claim 1, wherein in the coating layer,

the alkali metal is at least one selected from the group consisting of Li, Na, K, Rb, Cs and Fr;

the alkaline earth metal is at least one selected from the group consisting of Be, Mg, Ca, Sr, Ba and Ra;

The post-transition metals and metalloids in Groups 13 to 15 are one selected from the group consisting of Al, Ga, In, Sn, Tl, Pb, Bi, Po, B, Si, Ge, As, Sb, Te and At. more than;

The non-metal element in Groups 14 to 16 is a precursor particle for producing a cathode active material, characterized in that at least one selected from the group consisting of C, P, S and Se.

The precursor particle according to claim 1, wherein the coating layer contains Li.

The precursor particle according to claim 1, wherein the coating layer comprises a material having a composition represented by the following formula (2):

(1-vw)A ₂ CO ₃ *vAOH*wA ₂ O (2)

In the above formula,

0≤v≤1, 0≤w≤1, 0≤(1-v-w)≤1;

A is at least one alkali metal and/or alkaline earth metal.

The precursor particle according to claim 1, wherein the coating layer includes two or more different elements.

A precursor powder comprising the novel precursor particles for producing the positive electrode active material according to claim 1 .

The precursor powder according to claim 10, wherein the precursor powder comprises novel precursor particles having at least two or more different particle diameters.

12. A cathode active material, characterized in that produced by firing the precursor powder according to claim 10 or 11.

A secondary battery comprising the cathode active material according to claim 12 .