KR20220169775A - Precursor for positive electrode active material, manufacturing method of the same and manufacturing method of positivie electrode active material using the same - Google Patents

Abstract

The present invention relates to a positive electrode active material precursor capable of realizing a positive electrode active material in the form of single particles, and specifically, to a positive electrode active material precursor, a manufacturing method thereof, and a method for manufacturing a positive electrode active material using the same, wherein the positive electrode active material precursor is a composite transition metal oxide having a composition represented by chemical formula 1 disclosed in the present specification and satisfying chemical formula 1 disclosed in the present specification.

Description

Cathode active material precursor, manufacturing method thereof, and manufacturing method of cathode active material using the same

The present invention relates to a cathode active material precursor, a manufacturing method thereof, and a manufacturing method of a cathode active material using the same.

Recently, as technology development and demand for mobile devices and electric vehicles increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries having high energy density and voltage, long cycle life, and low self-discharge rate have been commercialized and widely used.

Lithium transition metal oxides such as lithium cobalt oxide such as LiCoO ₂ , lithium nickel oxide such as LiNiO ₂ , lithium manganese oxide such as LiMnO ₂ or LiMn ₂ O ₄ , and lithium iron phosphate oxide such as LiFePO ₄ as a cathode active material of a lithium secondary battery. have been developed, and recently, two or more transition metals such as Li[Ni _a Co _b Mn _c ]O ₂ , Li[Ni _a Co _b Al _c ]O ₂ , Li[Ni _a Co _b Mn _c Al _d ]O ₂ A lithium composite transition metal oxide containing a has been developed and is widely used.

Lithium transition metal oxides developed to date are typically prepared by mixing a transition metal hydroxide, a lithium-containing raw material, and optionally a doping raw material, and the like, followed by high-temperature heat treatment. At this time, in order to produce a lithium transition metal oxide in the form of a single particle, a method such as slightly increasing the temperature during high-temperature heat treatment is used.

However, a cathode active material in the form of a single particle manufactured by over-firing a transition metal hydroxide and a lithium-containing raw material has problems such as deterioration of long-term cycle characteristics when applied to a secondary battery.

The present invention is to solve the above problems, and to provide a cathode active material precursor capable of realizing a cathode active material in the form of a single particle having excellent long-term cycle characteristics when applied to a secondary battery.

And, it is intended to provide a manufacturing method of the positive electrode active material precursor.

In addition, it is intended to provide a method for manufacturing a cathode active material using the cathode active material precursor.

The present invention provides a cathode active material precursor that is a composite transition metal oxide having a composition represented by Formula 1 below and that satisfies Formula 1 below.

[Formula 1]

Ni _a Co _b M1 _c Zr _d M2 _e O

In Formula 1,

M1 is at least one selected from Mn and Al,

M2 is at least one selected from Nb, Ti, Mg, Ta, W, B, P, La, Y, V, Mo, Na, Ca, and Sc;

0.6≤a<1, 0<b<0.4, 0<c<0.4, 0<d≤0.2, 0≤e≤0.2, a+b+c+d+e=1,

[Equation 1]

.

.

In addition, the present invention mixes a composite transition metal hydroxide or a composite transition metal oxyhydroxide with a compound containing zirconium and hydroxide, and calcines (oxidation firing) at a temperature of 850 ° C to less than 1000 ° C to obtain a composite transition metal oxide cathode active material precursor It provides a method for producing a positive electrode active material precursor according to the present invention comprising the step of preparing.

In addition, the cathode active material precursor according to the present invention and a lithium-containing raw material are mixed, subjected to primary heat treatment at a temperature of greater than 800 ° C and less than 1000 ° C, and then secondary heat treatment at a temperature of greater than 650 ° C and less than 900 ° C to form single particles. Obtaining a lithium transition metal oxide of; provides a method for producing a positive electrode active material comprising a.

The cathode active material precursor according to the present invention is a composite transition metal oxide precursor, and the BET specific surface area value for the average particle diameter satisfies a specific value, thereby providing a cathode active material in the form of a single particle capable of improving long-term cycle characteristics of a secondary battery. can do.

1 is a SEM image of a positive electrode active material precursor of Example 1.
2 is a SEM image of the cathode active material precursor of Comparative Example 7.
3 is a SEM image of the cathode active material precursor of Comparative Example 8.
4 is a SEM image of the cathode active material of Example 1.
5 is a SEM image of the cathode active material of Comparative Example 1.
6 is XRD data of the positive electrode active material precursor of Example 1.

The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

In this specification, terms such as "comprise", "comprise" or "having" are intended to indicate that there is an embodied feature, number, step, component, or combination thereof, but one or more other features or numerals. However, it should be understood that it does not preclude the presence or addition of steps, components, or combinations thereof.

In the present specification, the average particle diameter (D ₅₀ ) may be defined as a particle diameter corresponding to 50% of the cumulative volume in the particle size distribution curve (graph curve of the particle size distribution) of each particle. The D ₅₀ can be measured using, for example, a laser diffraction method. The laser diffraction method is generally capable of measuring particle diameters of several millimeters in the submicron region, and can obtain results with high reproducibility and high resolution. The average particle diameter (D ₅₀ ) may be specifically measured using Microtrac's S3500.

In this specification, the term "on" means not only the case where a certain component is formed directly on top of another component, but also includes the case where a third component is interposed between these components.

In the present specification, the single particle form is a concept in contrast to the form of spherical secondary particles formed by aggregation of tens to hundreds of primary particles prepared by the conventional method, and each particle is independently and / or separated phase ), or may include a form in which 2 to 10 particles are attached to each other, or the form in which they are separated and / or dispersed from each other to form.

In the present specification, the primary particle refers to the smallest unit particle observed when measuring with a scanning electron microscope (SEM). Secondary particles refer to an aggregate, that is, a secondary structure, in which primary particles are aggregated by physical or chemical bonding between primary particles without intentional aggregation or assembling of the primary particles constituting the secondary particles.

In the present specification, the aspect ratio of primary particles means the ratio of the major axis length to the minor axis length of the primary particles (ie, major axis length/short axis length), and the cathode active material precursor is examined under a scanning electron microscope (SEM). It can be measured by obtaining the short axis length and the long axis length of the primary particles from the SEM picture obtained by observing with , and calculating the ratio.

In the present specification, the BET specific surface area is measured by the BET method, and specifically, it may be calculated from the nitrogen gas adsorption amount under liquid nitrogen temperature (77K) using BELSORP mini-II of BEL Japan.

Cathode Active Material Precursor

The positive electrode active material precursor according to the present invention is a complex transition metal oxide having a composition represented by Formula 1 below, and satisfies Formula 1 below.

[Formula 1]

Ni _a Co _b M1 _c Zr _d M2 _e O

In Formula 1,

M1 is at least one selected from Mn and Al,

M2 is at least one selected from Nb, Ti, Mg, Ta, W, B, P, La, Y, V, Mo, Na, Ca, and Sc;

0.6≤a<1, 0<b<0.4, 0<c<0.4, 0<d≤0.2, 0≤e≤0.2, a+b+c+d+e=1,

[Equation 1]

.

.

As a result of repeated research to develop a cathode active material having a single particle form capable of improving long-term cycle characteristics of a secondary battery, the inventors of the present invention are a composite transition metal oxide having a composition represented by Formula 1 as a precursor of the cathode active material, When using the positive electrode active material precursor satisfying Formula 1, it was found that cycle characteristics of a secondary battery including a positive electrode active material prepared using the precursor could be improved, and the present invention was completed.

The cathode active material precursor according to the present invention has a composition represented by Chemical Formula 1, and is advantageous in realizing a single particle form by maximizing the growth of primary particles during heat treatment for manufacturing a cathode active material. On the other hand, when the cathode active material precursor is out of the composition represented by Formula 1, more energy is required to realize a single particle form during heat treatment for manufacturing the cathode active material, so heat treatment must be performed at a high temperature, resulting in fairness and stability. There is a problem with this degradation.

The a means the atomic fraction of nickel among the metal elements in the precursor, and may be 0.6≤a<1, 0.6≤a≤0.98, or 0.7≤a≤0.95.

The b refers to the atomic fraction of cobalt among metal elements in the precursor, and may be 0<b≤0.4, 0.01≤b≤0.4, or 0.01≤b≤0.3.

The c denotes an atomic fraction of element M1 among metal elements in the precursor, and may be 0<c≤0.4, 0.01≤c≤0.4, or 0.01≤c≤0.3.

The d represents the atomic fraction of the zirconium element among the metal elements in the precursor, and may be 0<d≤0.2, 0<d≤0.1, or 0<d≤0.05.

The e denotes an atomic fraction of element M2 among metal elements in the precursor, and may be 0≤e≤0.2, 0≤e≤0.1, or 0≤e≤0.05.

In addition, the cathode active material precursor according to the present invention satisfies Equation 1, and thus has an advantage in that primary particles are aggregated and increased in size during the crystal growth process, and the boundary between particles is reduced to uniformly grow the particles. On the other hand, when the positive electrode active material precursor does not satisfy the value according to Equation 1, specifically, when the value according to Equation 1 is 0.020 or less, more energy is used to realize a single particle form during heat treatment for manufacturing the positive electrode active material. Since heat treatment must be performed at a high temperature, there is a problem in that structural stability is deteriorated. In addition, when the value according to Equation 1 is greater than 0.2, primary particles do not grow and many spaces are formed therein, so there is a problem in that particle growth does not proceed uniformly during heat treatment for manufacturing a cathode active material later.

In Equation 1, the BET specific surface area may be 0.1 m ² /g to 5 m ² /g, preferably 0.15 m ² /g to 3 m ² /g, and more preferably 0.2 m ² /g to 1 m ² /g. there is. When the BET specific surface area is within the above range, since the distance between the primary particles is not widened and the primary particles are in close contact with each other, the number of grain boundaries is reduced, which is advantageous in producing a single particle form.

In Equation 1, the average particle diameter (D ₅₀ ) may be 1 μm to 50 μm, preferably 2 μm to 20 μm, and more preferably 3 μm to 15 μm.

According to the present invention, the positive electrode active material precursor may include a NiO phase and an α-MnO ₂ phase. In this case, it has an energetically more stable structure than the transition metal hydroxide, so that an explosive reaction does not occur during firing and uniform firing is possible.

Manufacturing method of cathode active material precursor

The method for producing a precursor of a cathode active material according to the present invention mixes a composite transition metal hydroxide or a composite transition metal oxyhydroxide with a compound containing zirconium and hydroxide, and calcinations (oxidation firing) at a temperature of 850 ° C to less than 1000 ° C to achieve complex transition Preparing a metal oxide positive electrode active material precursor; includes. The compound containing zirconium and hydroxide can maximize the growth of primary particles by expressing a flux effect, and as a result, it is easy to manufacture a single-particle cathode active material.

The positive active material precursor prepared according to the manufacturing method of the positive active material precursor is the positive active material precursor according to the present invention. That is, it is a complex transition metal oxide having a composition represented by Formula 1, and satisfies Formula 1 above.

When the composite transition metal oxide cathode active material precursor is prepared in a dry manner as in the present invention, the composite transition metal hydroxide or composite transition metal oxyhydroxide is prepared by using an aqueous solution containing a compound containing zirconium and hydroxide by a method such as spray drying. Processability may be improved compared to the case where the composite transition metal oxide cathode active material precursor is wet-prepared by coating it with a compound containing peroxide and then firing it. And, since Zr(OH) ₄ is insoluble in water, it is not suitable for spray drying.

Hereinafter, a method for manufacturing a cathode active material precursor will be described in detail.

First, a composite transition metal hydroxide or a composite transition metal oxyhydroxide is mixed with a compound containing zirconium and hydroxide.

According to the present invention, the composite transition metal hydroxide or the composite transition metal oxyhydroxide is in the form of secondary particles formed by aggregation of primary particles, and the primary particles have an aspect ratio of 3 to 15, specifically 5 to 8 days. When the aspect ratio of the primary particle satisfies the above range, there is an effect of forming a short lithium movement path inside and outside the particle.

The complex transition metal hydroxide may have a composition represented by Formula 2 below, and the complex transition metal oxyhydroxide may have a composition represented by Formula 3 below.

[Formula 2]

Ni _a2 Co _b2 M1 _c2 M2 _e2 (OH) ₂

In Formula 2,

M1 is at least one selected from Mn and Al,

M2 is at least one selected from Nb, Ti, Mg, Ta, W, B, P, La, Y, V, Mo, Na, Ca, and Sc;

0.6≤a2<1, 0<b2<0.4, 0<c2<0.4, 0≤e2≤0.2, a2+b2+c2+e2=1,

[Formula 3]

Ni _a2 Co _b2 M1 _c2 M2 _e2 O OH

In Formula 3,

M1 is at least one selected from Mn and Al,

M2 is at least one selected from Nb, Ti, Mg, Ta, W, B, P, La, Y, V, Mo, Na, Ca, and Sc;

0.6≤a2<1, 0<b2<0.4, 0<c2<0.4, 0≤e2≤0.2, and a2+b2+c2+e2=1.

According to the present invention, the compound containing zirconium and hydroxide may be Zr(OH) ₄ . In this case, since the melting point of the compound is high, the particles can be uniformly grown. In addition, the size of the primary particles can be grown larger. Accordingly, there is an advantage in that a lot of energy is not required to realize a single particle form during heat treatment for manufacturing the cathode active material.

On the other hand, in the case of using zirconium sulfate, etc., rather than the compound containing zirconium and hydroxide, as a zirconium raw material-containing material, it is difficult to expect a flux effect due to the low melting point of the compound, and sulfuric acid, etc. There is a problem that impurities remain on the surface.

The compound containing zirconium and hydroxide is 0.01 part by weight to 0.1 part by weight, specifically 0.01 part by weight to 0.9 part by weight, more specifically 0.01 part by weight to 0.87 part by weight based on 100 parts by weight of the complex transition metal hydroxide or the complex transition metal oxyhydroxide. It may be added in an amount of parts by weight. When the content of the compound containing zirconium and hydroxide is within the above range, the flux effect can be maximized while preventing a decrease in capacity or long-term cycle characteristics.

As described above, when a mixture of a composite transition metal hydroxide or a composite transition metal oxyhydroxide mixed with a compound containing zirconium and hydroxide is fired at a temperature of 850 ° C to less than 1000 ° C, the composite transition metal oxide cathode active material according to the present invention precursors can be obtained. On the other hand, when firing at a temperature of less than 850 ° C., there is a problem in that primary particles do not greatly grow due to low temperature, and when firing at a temperature of 1000 ° C. or higher, there is a problem in that transition metal elution is severe.

Cathode active material manufacturing method

In the method for manufacturing a positive active material according to the present invention, the positive active material precursor according to the present invention is mixed with a lithium-containing raw material, subjected to primary heat treatment at a temperature of greater than 800 °C and less than 1000 °C, and then heated at a temperature of greater than 650 °C and less than 900 °C. Secondary heat treatment to obtain lithium transition metal oxide in the form of single particles; includes.

On the other hand, when the first heat treatment is performed at a temperature of 800 ° C or lower, the reactivity with the lithium compound is reduced, the remaining lithium compound increases, and there is a problem that the form of a single particle is not formed, and when the first heat treatment is performed at a temperature of 900 ° C or higher , there is a problem in that capacity decreases because it does not have a stable layered structure and nickel ions hop into the lithium layer to hinder the movement of lithium.

And, in the case of the secondary heat treatment at a temperature of 650 ° C or less, there is a problem that the unstable cubic or spinel structure existing after the first heat treatment does not change to a stable layered structure, and in the case of the secondary heat treatment at a temperature of 900 ° C or higher, the first heat treatment There is a problem in that the capacity decreases by making the later stable structures into unstable structures.

The first heat treatment temperature may be higher than the second heat treatment temperature. When the heat treatment temperature is high, lithium or metal ions may be eluted. After the first heat treatment at a higher temperature, the second heat treatment is performed at a lower temperature than the first heat treatment (a temperature capable of stabilizing the particles), resulting in unstable cubic or The spinel structure can be transformed into a stable layered structure. In this case, the difference between the first heat treatment temperature and the second heat treatment temperature may be more than 50 ° C and less than 200 ° C, specifically 70 ° C to 200 ° C, 70 ° C to 170 ° C.

The lithium-containing raw material may include at least one selected from lithium hydroxide hydrate, lithium carbonate, lithium nitrate, and lithium oxide. The lithium-containing raw material may be specifically, lithium hydroxide hydrate, more specifically, LiOH·H ₂ O. In this case, the reactivity between a precursor having a high atomic fraction of nickel among metal elements in the precursor and a raw material containing lithium may be improved.

When preparing the positive electrode active material, the positive electrode active material precursor and the lithium-containing raw material may be mixed in a molar ratio of 1:1.02 to 1:1.2, specifically 1:1.02 to 1:1.1, and more specifically 1:1.02 to 1:1.07. can When the lithium-containing raw material is mixed below the above range, there is a concern that the capacity of the cathode active material to be produced may decrease, and when the lithium-containing raw material is mixed beyond the above range, unreacted Li remains as a by-product, and the capacity After deterioration and firing, separation of cathode active material particles (causation of cathode active material coalescence) may occur.

The first heat treatment and the second heat treatment may be performed in an air or oxygen atmosphere, respectively. In this case, it is possible to increase the reactivity, uniformly sinter the particles, and increase the degree of crystallinity.

The first heat treatment may be performed for 3 hours to 15 hours, and the second heat treatment may be performed for 5 hours to 20 hours. When the first heat treatment time and the second heat treatment time are within the above ranges, the lithium source reacts for a sufficient time to increase crystallinity through rearrangement of atoms and reduce defects.

In the cathode active material manufacturing method, when mixing a cathode active material precursor and a lithium-containing raw material, a doping element-containing material is mixed together and heat-treated to prepare a cathode active material doped with a doping element.

In addition, the cathode active material manufacturing method may prepare a cathode active material in which a coating layer is formed on the lithium transition metal oxide by mixing a raw material containing a coating element with the prepared lithium transition metal oxide in the form of a single particle and performing secondary heat treatment.

The positive electrode active material prepared according to the positive electrode active material manufacturing method may be a lithium transition metal oxide in the form of a single particle and have a composition represented by Chemical Formula 4 below.

[Formula 4]

Li _x [Ni _a' Co _b' M1 _c' Zr _d' M3 _f ]O ₂

In Formula 4,

M1 is at least one element selected from Mn and Al,

M3 is at least one selected from Nb, Ti, Mg, Ta, W, B, P, La, Y, V, Mo, Na, Ca, and Sc;

0.9≤x≤1.2, 0.6≤a'<1, 0<b'≤0.4, 0<c'≤0.4, 0<d'≤0.2, 0≤f≤0.2, a'+b'+c'+d '+f=1.

anode

In addition, the present invention may provide a cathode for a lithium secondary battery including the cathode active material prepared by the above-described method.

Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and including the positive electrode active material.

The positive current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon, nickel, titanium on the surface of aluminum or stainless steel. , those surface-treated with silver, etc. may be used. In addition, the cathode current collector may have a thickness of typically 3 μm to 500 μm, and adhesion of the cathode active material may be increased by forming fine irregularities on the surface of the current collector. For example, it may be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics.

The positive electrode active material layer may include a conductive material and a binder together with the positive electrode active material.

The cathode active material may be included in an amount of 80 wt% to 99 wt%, more specifically, 85 wt% to 98 wt%, based on the total weight of the cathode active material layer. When included in the above content range, excellent capacity characteristics may be exhibited.

The conductive material is used to impart conductivity to the electrode, and in the battery, any material that does not cause chemical change and has electronic conductivity can be used without particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of them alone or a mixture of two or more may be used. The conductive material may be included in an amount of 1 wt% to 30 wt% based on the total weight of the cathode active material layer.

The binder serves to improve adhesion between particles of the positive electrode active material and adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC) ), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, and the like may be used alone or in a mixture of two or more of them. The binder may be included in an amount of 1 wt% to 30 wt% based on the total weight of the cathode active material layer.

The positive electrode may be manufactured according to a conventional positive electrode manufacturing method except for using the positive electrode active material. Specifically, the composition for forming a cathode active material layer prepared by dissolving or dispersing the above-described cathode active material and, optionally, a binder and a conductive material in a solvent may be coated on a cathode current collector, followed by drying and rolling. In this case, the types and contents of the positive electrode active material, the binder, and the conductive material are as described above.

The solvent may be a solvent commonly used in the art, and dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water and the like, and one type alone or a mixture of two or more types of these may be used. The amount of the solvent used is enough to dissolve or disperse the positive electrode active material, conductive material, and binder in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity capable of exhibiting excellent thickness uniformity during subsequent coating for manufacturing the positive electrode. Do.

Alternatively, the positive electrode may be manufactured by casting the composition for forming the positive electrode active material layer on a separate support and then laminating a film obtained by peeling from the support on a positive electrode current collector.

lithium secondary battery

In addition, the present invention can manufacture an electrochemical device including the anode. The electrochemical device may be specifically a battery, a capacitor, and the like, and more specifically, may be a lithium secondary battery.

The lithium secondary battery specifically includes a positive electrode, a negative electrode positioned opposite to the positive electrode, and a separator and an electrolyte interposed between the positive electrode and the negative electrode, and the positive electrode is the same as described above, so a detailed description is omitted, Hereinafter, only the remaining configurations will be described in detail.

In addition, the lithium secondary battery may optionally further include a battery container accommodating the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member sealing the battery container.

In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

The anode current collector is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, it is formed on the surface of copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel. A surface treated with carbon, nickel, titanium, silver, or the like, an aluminum-cadmium alloy, or the like may be used. In addition, the negative electrode current collector may have a thickness of typically 3 μm to 500 μm, and like the positive electrode current collector, fine irregularities may be formed on the surface of the current collector to enhance bonding strength of the negative electrode active material. For example, it may be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics.

The anode active material layer optionally includes a binder and a conductive material together with the anode active material.

A compound capable of reversible intercalation and deintercalation of lithium may be used as the anode active material. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of being alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides capable of doping and undoping lithium, such as SiO _β (0<β<2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; or a composite including the metallic compound and the carbonaceous material, such as a Si—C composite or a Sn—C composite, and any one or a mixture of two or more of these may be used. In addition, a metal lithium thin film may be used as the anode active material. In addition, as the carbon material, both low crystalline carbon and high crystalline carbon may be used. Soft carbon and hard carbon are typical examples of low crystalline carbon, and high crystalline carbon includes amorphous, platy, scaly, spherical or fibrous natural graphite, artificial graphite, or kish graphite. graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch High-temperature calcined carbon such as derived cokes is representative.

The negative electrode active material may be included in an amount of 80% to 99% by weight based on the total weight of the negative electrode active material layer.

The binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and may be typically added in an amount of 0.1% to 10% by weight based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluorocarbons, roethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, various copolymers thereof, and the like.

The conductive material is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10% by weight or less, specifically 5% by weight or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The negative electrode active material layer is prepared by applying a negative electrode active material and, optionally, a negative electrode composite prepared by dissolving or dispersing a binder and a conductive material in a solvent on a negative electrode current collector and drying the negative electrode composite, or casting the negative electrode composite on a separate support. Then, it can be manufactured by laminating the film obtained by peeling from the support on the negative electrode current collector.

On the other hand, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ion movement. Anything that is normally used as a separator in a lithium secondary battery can be used without particular limitation, especially for the movement of ions in the electrolyte. It is preferable to have low resistance to the electrolyte and excellent ability to absorb the electrolyte. Specifically, a porous polymer film, for example, a porous polymer film made of polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylate copolymer, or these A laminated structure of two or more layers of may be used. In addition, conventional porous non-woven fabrics, for example, non-woven fabrics made of high-melting glass fibers, polyethylene terephthalate fibers, and the like may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may be selectively used in a single-layer or multi-layer structure.

In addition, the electrolyte used in the present invention includes organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries, and are limited to these. it is not going to be

Specifically, the electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon-based solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate, PC) and other carbonate-based solvents; alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a straight-chain, branched or cyclic hydrocarbon group having 2 to 20 carbon atoms and may contain a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; Alternatively, sulfolane or the like may be used. Among them, carbonate-based solvents are preferred, and cyclic carbonates (eg, ethylene carbonate or propylene carbonate, etc.) having high ion conductivity and high dielectric constant capable of increasing the charge and discharge performance of batteries, and low-viscosity linear carbonate-based compounds ( For example, a mixture of ethyl methyl carbonate, dimethyl carbonate or diethyl carbonate) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:1 to about 1:9, the performance of the electrolyte may be excellent.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ or the like may be used. The concentration of the lithium salt is preferably used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so excellent electrolyte performance can be exhibited, and lithium ions can move effectively.

In addition to the above electrolyte components, the electrolyte may include, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, and triglycerides for the purpose of improving battery life characteristics, suppressing battery capacity decrease, and improving battery discharge capacity. Ethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imida One or more additives such as zolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol or aluminum trichloride may be further included. In this case, the additive may be included in an amount of 0.1% to 5% by weight based on the total weight of the electrolyte.

As described above, since the lithium secondary battery including the cathode active material according to the present invention stably exhibits excellent cycle characteristics, it is suitable for use in portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles (HEVs). It is useful in fields such as electric vehicles and the like.

Accordingly, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack may include a power tool; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); Alternatively, it may be used as a power source for one or more medium or large-sized devices among power storage systems.

The appearance of the lithium secondary battery of the present invention is not particularly limited, but may be a cylindrical shape using a can, a prismatic shape, a pouch shape, or a coin shape.

The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but also can be preferably used as a unit cell in a medium-large battery module including a plurality of battery cells.

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

Examples and Comparative Examples

Example 1

Ni _0.88 Co _0.05 Mn _0.07 (OH) ₂ Mixed 0.698 parts by weight of Zr(OH) ₄ with respect to 100 parts by weight of a composite transition metal hydroxide (D ₅₀ : 9.21 μm, BET specific surface area: 4.13 m ² /g) having a composition represented by and calcined at 950° C. for 10 hours in an air atmosphere to prepare a cathode active material precursor, which is a composite transition metal oxide having a composition represented by Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O. At this time, the BET specific surface area (using BELSORP mini-II from BEL Japan) and average particle diameter (D ₅₀ ) (using S3500 from Microtrac) of the positive active material precursor were measured and shown in Table 1 below.

The cathode active material precursor and LiOH were mixed so that the molar ratio of (Ni+Co+Mn+Zr):Li was 1:1.05, followed by primary heat treatment at 950°C for 4 hours under an air atmosphere, and then at 780°C for 10 hours. A cathode active material having a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ and a lithium transition metal oxide in the form of a single particle was prepared by secondary heat treatment.

Example 2 (Example different from Example 1 only in the first heat treatment temperature)

A positive electrode active material having a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ in the same manner as in Example 1, except that the first heat treatment temperature was adjusted to 850 ° C, and is a lithium transition metal oxide in the form of single particles. was manufactured.

Example 3 (An example different from Example 1 only in the second heat treatment temperature)

A positive electrode active material having a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ in the same manner as in Example 1, except that the secondary heat treatment temperature was adjusted to 850 ° C, and is a lithium transition metal oxide in the form of single particles. was manufactured.

Example 4 (Example different from Example 1 only in firing temperature)

Li 1.05 Ni 0.876 Co 0.05 Mn 0.07 Zr 0.004 O 2 It has a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ in the same manner as in Example 1, except that the cathode active material precursor was prepared by adjusting the firing temperature to 850 ° C. An oxide active material was prepared. At this time, the BET specific surface area and average particle diameter (D ₅₀ ) of the positive electrode active material precursor prepared in Example 4 were measured and are shown in Table 1 below.

Comparative Example 1 (In case of using hydroxide as a cathode active material precursor)

A composite transition metal hydroxide having a composition represented by Ni _0.88 Co _0.05 Mn _0.07 (OH) ₂ (D ₅₀ : 9.21 μm, BET specific surface area: 4.13 m ² /g), Zr(OH) ₄ , LiOH (Ni+Co+ Mn) : Zr : Li was mixed so that the molar ratio was 1:0.004:1.05, followed by primary heat treatment at 950 ° C for 4 hours in an air atmosphere, and then secondary heat treatment at 780 ° C for 10 hours to obtain Li _1.05 Ni _0.876 Co _0.05 A positive electrode active material having a composition represented by Mn _0.07 Zr _0.004 O ₂ and a lithium transition metal oxide in the form of secondary particles formed by aggregation of primary particles was prepared.

Comparative Example 2 (Zr(OH) ₄ if zirconium sulfate was used instead)

A composite transition metal hydroxide (D ₅₀ : 9.21 μm, BET specific surface area: 4.13 m ² /g) having a composition represented by Ni _0.88 Co _0.05 Mn _0.07 (OH) ₂ was mixed with zirconium sulfate and heated at 950° C. By firing for a period of time, a cathode active material precursor, which is a composite transition metal oxide having a composition represented by Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O, was prepared. At this time, the BET specific surface area and average particle diameter (D ₅₀ ) of the positive electrode active material precursor were measured and shown in Table 1 below.

The cathode active material precursor and LiOH were mixed so that the molar ratio of (Ni+Co+Mn+Zr):Li was 1:1.05, followed by primary heat treatment at 950°C for 4 hours under an air atmosphere, and then at 780°C for 10 hours. A cathode active material having a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ and a lithium transition metal oxide in the form of a single particle was prepared by secondary heat treatment.

Comparative Example 3 (Comparative Example different from Example 1 only in the first heat treatment temperature)

It has a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ in the same manner as in Example 1, except that the temperature of the first heat treatment was adjusted to 800 ° C., in the form of secondary particles formed by aggregation of primary particles. A positive electrode active material, which is a lithium transition metal oxide, was prepared.

Comparative Example 4 (Comparative Example different from Example 1 only in the first heat treatment temperature)

A cathode active material having a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ in the same manner as in Example 1, except that the first heat treatment temperature was adjusted to 1000° C., and is a lithium transition metal oxide in the form of single particles. was manufactured.

Comparative Example 5 (An Example different from Example 1 only in the secondary heat treatment temperature)

A cathode active material having a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ in the same manner as in Example 1, except that the secondary heat treatment temperature was adjusted to 650° C., and is a lithium transition metal oxide in single particle form. was manufactured.

Comparative Example 6 (An Example different from Example 1 only in the second heat treatment temperature)

A cathode active material having a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ in the same manner as in Example 1, except that the secondary heat treatment temperature was adjusted to 900 ° C, and is a lithium transition metal oxide in the form of single particles. was manufactured.

Comparative Example 7 (BET specific surface area of oxide precursor/D ₅₀ Comparative example with a value of 0.02)

A positive electrode active material having a composition represented by Li _1.05 Ni _0.876 Co _0.05 Mn _0.07 Zr _0.004 O ₂ and being a lithium transition metal oxide in the form of single particles was prepared in the same manner as in Example 1, except that the oxidation firing temperature was adjusted to 1000 ° C. manufactured.

Comparative Example 8 (BET specific surface area of oxide precursor/D ₅₀ Comparative example with a value of 0.249)

Ni _0.95 Co _0.02 Mn _0.03 (OH) ₂ A composite transition metal hydroxide (D ₅₀ : 3.3 μm, BET specific surface area: 9.813 m ² /g) having a composition represented by Zr(OH) ₄ was mixed with 850 A cathode active material precursor, which is a composite transition metal oxide having a composition represented by Ni _0.946 Co _0.02 Mn _0.03 Zr _0.004 O, was prepared by firing at °C for 10 hours. At this time, the BET specific surface area and average particle diameter (D ₅₀ ) of the positive electrode active material precursor were measured and shown in Table 1 below.

The cathode active material precursor and LiOH were mixed so that the molar ratio of (Ni+Co+Mn+Zr):Li was 1:1.05, followed by primary heat treatment at 950°C for 4 hours under an air atmosphere, and then at 780°C for 10 hours. A cathode active material having a composition represented by Li _1.05 Ni _0.946 Co _0.02 Mn _0.03 Zr _0.004 O ₂ and a lithium transition metal oxide in the form of a single particle was prepared by secondary heat treatment.

Oxidation firing temperature
(℃) 1st heat treatment temperature
(℃) 2nd heat treatment temperature
(℃) BET specific surface area of oxide precursor
(m ² /g) D ₅₀ of oxide precursor
(μm) BET specific surface area/D ₅₀ of oxide precursor note Example 1 950 950 780 0.2386 9.12 0.028 Example 2 950 850 780 0.2386 9.12 0.028 Example 3 950 950 850 0.2386 9.12 0.028 Example 4 850 950 780 1.0202 9.62 0.106 Comparative Example 1 - 950 780 - - - Hydroxide is used as a precursor for the cathode active material Comparative Example 2 950 950 780 0.2282 11.26 0.02 Use zirconium sulfate instead of Zr(OH) ₄ Comparative Example 3 950 800 780 0.2386 9.12 0.028 Comparative Example 4 950 1000 780 0.2386 9.12 0.028 Comparative Example 5 950 950 650 0.2386 9.12 0.028 Comparative Example 6 950 950 900 0.2386 9.12 0.028 Comparative Example 7 1000 950 780 0.2081 10.2 0.020 Comparative Example 8 850 950 780 0.7705 3.1 0.249

Experimental example

Experimental Example 1

SEM images of the cathode active material precursors of Example 1 and Comparative Examples 7 and 8 were measured using an SEM (FEI Corporation, Inspect F), and the SEM images of the cathode active material precursors of Example 1 are shown in FIG. 1, Comparative Example 7 , SEM images of the cathode active material precursors of 8 are shown in FIGS. 2 and 3, respectively.

In addition, SEM images of the cathode active materials of Example 1 and Comparative Example 1 were measured, and are shown in FIGS. 4 and 5, respectively.

Experimental Example 2

Using XRD (Bruker, D4 Endeavor), XRD data of the positive electrode active material precursor of Example 1 was obtained, and it is shown in FIG. 6 . Referring to FIG. 6 , it can be seen that the positive electrode active material precursor of Example 1 includes a NiO phase and an α-MnO ₂ phase.

Claims (10)

A complex transition metal oxide having a composition represented by Formula 1 below,
A cathode active material precursor that satisfies Equation 1 below:
[Formula 1]
Ni _a Co _b M1 _c Zr _d M2 _e O
In Formula 1,
M1 is at least one selected from Mn and Al,
M2 is at least one selected from Nb, Ti, Mg, Ta, W, B, P, La, Y, V, Mo, Na, Ca, and Sc;
0.6≤a<1, 0<b<0.4, 0<c<0.4, 0<d≤0.2, 0≤e≤0.2, a+b+c+d+e=1,
[Equation 1]

.
The method of claim 1,
The cathode active material precursor includes a NiO phase and an α-MnO ₂ phase.
The method of claim 1,
A positive electrode active material precursor having a BET specific surface area of 0.1 m ² /g to 5 m ² /g.
The method of claim 1,
A cathode active material precursor having an average particle diameter (D ₅₀ ) of 1 μm to 50 μm.
Claim 1 comprising: preparing a composite transition metal oxide cathode active material precursor by mixing a composite transition metal hydroxide or composite transition metal oxyhydroxide with a compound containing zirconium and hydroxide, and firing at a temperature of 850° C. to less than 1000° C. Method for producing a positive electrode active material precursor according to.
The method of claim 5,
The composite transition metal hydroxide or the composite transition metal oxyhydroxide is in the form of secondary particles formed by aggregation of primary particles,
The primary particle is a method for producing a positive electrode active material precursor having an aspect ratio of 3 to 15.
The method of claim 5,
The compound containing zirconium and hydroxide is Zr (OH) ₄ Method of producing a positive electrode active material precursor.
The cathode active material precursor according to claim 1 is mixed with a lithium-containing raw material, subjected to primary heat treatment at a temperature of greater than 800°C and less than 1000°C, and then secondary heat treated at a temperature of greater than 650°C and less than 900°C to form lithium in single particle form. Obtaining a transition metal oxide; method of producing a positive electrode active material comprising a.
The method of claim 8,
The first heat treatment temperature is a method for producing a cathode active material that is higher than the second heat treatment temperature.
The method of claim 9,
The difference between the first heat treatment temperature and the second heat treatment temperature is greater than 50 ° C. and less than 200 ° C. Method for producing a positive electrode active material.

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