KR101872470B1 - Electrode active material, preparation method thereof, and electrode and lithium battery containing the same - Google Patents

Abstract

A core capable of intercalating and deintercalating lithium; And a surface treatment layer formed on at least a portion of the core, wherein the surface treatment layer comprises a lithium-free oxide having a spinel structure, wherein the X- Ray diffraction spectrum of the electrode active material having a peak intensity with respect to the impurity phase being equal to or lower than a noise level, a method for producing the electrode active material, and an electrode and a lithium battery using the electrode active material.

Description

TECHNICAL FIELD [0001] The present invention relates to an electrode active material, a method of manufacturing the electrode active material, and an electrode and a lithium battery employing the electrode active material,

An electrode active material, a manufacturing method thereof, and an electrode and a lithium battery employing the same.

In order to meet the miniaturization and high performance of various devices, besides the miniaturization and weight reduction of lithium batteries, higher energy density is becoming important. That is, high-voltage and high-capacity lithium batteries are becoming important.

A high-voltage and high-capacity cathode active material has been studied for realizing a lithium battery conforming to the above-mentioned use.

Conventional high-voltage and high-capacity cathode active materials have side reactions such as elution of transition metals and gas generation at high temperature and / or high voltage range of 4.4 V or higher. The performance of the battery deteriorated in a high temperature and high voltage environment due to elution or side reaction of the transition metal.

Therefore, there is a demand for a method capable of preventing performance deterioration of the battery in a high-temperature and high-voltage environment.

One aspect is to provide an electrode active material capable of preventing performance deterioration of the battery under high temperature and high voltage.

Another aspect is to provide an electrode comprising the electrode active material.

Another aspect is to provide a lithium battery employing the electrode.

Another aspect provides a method for producing the electrode active material.

On one side

A core capable of intercalating and deintercalating lithium; And

And a surface treatment layer formed on at least a portion of the core,

Wherein the surface treatment layer comprises a lithium-free oxide having a spinel structure,

An X-ray diffraction spectrum using a Cu-K? Line for the lithium-free oxide provides an electrode active material having a peak intensity with respect to the impurity phase being not higher than a noise level.

According to another aspect, there is provided an electrode comprising the electrode active material.

According to another aspect, there is provided a lithium battery including the electrode.

According to another aspect

Mixing a core comprising an electrode active material with lithium-free oxide particles having a spinel structure; And

And a step of forming a surface treatment layer containing a lithium-free oxide on the core by a dry method.

According to one aspect of the present invention, a core capable of lithium storage and release has a spinel structure and is surface-treated with a lithium-free oxide free from impurities, thereby improving the high-temperature stability, high-temperature lifetime, and high-rate characteristics of the lithium battery.

1 (a) shows XRD (X-ray diffraction) test results for SnZn ₂ O ₄ prepared in Comparative Preparation Example 1. FIG.
1 (b) shows the XRD test results for SnZn ₂ O ₄ prepared in Preparation Example 1.
2 is a SEM photograph of SnZn ₂ O ₄ prepared in Preparation Example 1.
3 is a SEM photograph of the LiNi _0.5 Mn _1.5 O ₄ powder used in Example 1. Fig.
4 is a SEM photograph of the cathode active material prepared in Example 1. Fig.
5 shows the results of high-rate characteristics tests of lithium batteries of Examples 97 to 98 and Comparative Example 5.
6 is a schematic diagram of a lithium battery according to an embodiment.

Hereinafter, an electrode active material according to exemplary embodiments, a method of manufacturing the electrode active material, and an electrode and a lithium battery including the same will be described in more detail.

The electrode active material according to an embodiment includes a core capable of intercalating and deintercalating lithium; And a surface treatment layer formed on at least a portion of the core, wherein the surface treatment layer comprises a lithium-free oxide having a spinel structure, wherein the X- Ray diffraction spectrum, the peak intensity for the impurity phase is below the noise level of the X-ray diffraction spectrum.

The intensity of the diffraction peak with respect to the impurity phase in the X-ray diffraction spectrum is below the noise level because the intensity of the diffraction peak relative to the impurity phase in the X-ray diffraction spectrum is lower than the noise level forming the baseline, It means that no diffraction peak is detected. Noise level refers to the X-ray scattering inevitably obtained from the scattering of the surrounding environment such as air and water, regardless of the X-ray scattering obtained from the target material.

That is, the surface treatment layer may be formed on part or all of the core surface by treating at least a portion of the surface of the core capable of intercalating and deintercalating lithium with a lithium-free oxide having a spinel structure and substantially no impurity phase. It is apparent to those skilled in the art that the expression of the surface treatment layer may alternatively be expressed as a coating layer. The impurity phase means an image that does not correspond to a spinel crystal (pahse).

Since the lithium-free oxide having the spinel structure substantially contains no impurities, side reactions due to the impurity phase during charge and discharge can be suppressed.

Hereinafter, the lithium-free oxide having a spinel structure is an oxide substantially free of the impurity phase unless otherwise specified.

The lithium-free oxide having the spinel structure may be highly crystalline. That is, the lithium-free oxide having a spinel structure and highly crystalline has a spinel structure in a X-ray diffraction spectrum using a Cu-K? Line, and has a sharp diffraction peak Lt; / RTI > The stability of the electrode active material at high voltage can be improved by having the lithium-free oxide have a high crystallinity.

For example, the lithium-free oxide has a diffraction peak with respect to the (311) plane at 2θ = 35.5 ± 2.0 ° in an X-ray diffraction spectrum using a Cu-Kα line, and the half width of the diffraction peak (FWHM , Full Width at Half Maximum) may be less than 0.3 degrees. For example, the lithium-free oxide has a diffraction peak with respect to the (311) plane at 2θ = 35.5 ± 2.0 ° in an X-ray diffraction spectrum using a Cu-Kα line, and the half width of the diffraction peak (FWHM ) May be 0.220 DEG to 0.270 DEG.

Since the lithium-free oxide having the spinel structure does not intercalate and deintercalate lithium, the oxide-containing surface treatment layer can serve as a protective layer of the core, for example, have. That is, the surface treatment layer can suppress the side reaction between the core and the electrolyte. In addition, the surface treatment layer may prevent the transition metal from leaching from the core capable of occluding and releasing lithium.

The lithium-free oxide having the spinel structure is an oxide including at least two metals other than lithium or a metalloid element, and can be used as long as it has a spinel crystal structure and has no highly crystalline and / or impurity phase.

The lithium-free oxide having the spinel structure may be an oxide having a conventional general salt crystal structure, for example, NaCl, CaO, FeO; Oxygen bond is stronger than that of an oxide having a corundum crystal structure such as Al ₂ O ₃ , Fe ₂ O ₃ , FeTiO ₃ , MgO, etc. to form a stable surface treatment layer even under high temperature and high voltage conditions .

For example, the lithium-free oxide may be at least one selected from oxides represented by the following general formula (1)

≪ Formula 1 >

AB ₂ O ₄

Wherein A is selected from the group consisting of Sn, Mg, Mo, Cu, Zn, Ti, Ni, Ca, Fe, V, Pb, Co, Ge, Cd, Hg, Sr, Mn, Al, And B is at least one selected from the group consisting of Mg, Zn, Al, V, Mn, Ga, Cr, Fe, Rh, Ni, In, Co and Mn.

For example, the lithium-free oxide is _{SnMg 2 O 4, SnZn 2 O} 4, MgAl 2 O 4, MoAl 2 O 4, CuAl 2 O 4, ZnAl 2 O 4, ZnV 2 O 4, TiMn 2 O 4 _{, ZnMn 2 O 4, NiAl 2} O 4, MgGa 2 O 4, ZnGa 2 O 4, CaGa 2 O 4, TiMg 2 O 4, VMg 2 O 4, MgV 2 O 4, FeV 2 O 4, ZnV 2 O 4 _{, MgCr 2 O 4, MnCr 2} O 4, FeCr 2 O 4, CoCr 2 O 4, NiCr 2 O 4, CuCr 2 O 4, ZnCr 2 O 4, CdCr 2 O 4, TiMn 2 O 4, ZnMn 2 O 4 _{, MgFe 2 O 4, TiFe 2} O 4, MnFe 2 O 4, CoFe 2 O 4, NiFe 2 O 4, CuFe 2 O 4, ZnFe 2 O 4, CdFe 2 O 4, AlFe 2 O 4, PbFe 2 O 4 _{, MgCo 2 O 4, TiCo 2} O 4, ZnCo 2 O 4, SnCo 2 O 4, FeNi 2 O 4, GeNi 2 O 4, MgRh 2 O 4, ZnRh 2 O 4, TiZn 2 O 4, SrAl 2 O 4 _{, CrAl 2 O 4, MoAl 2} O 4, FeAl 2 O 4, CoAl 2 O 4, MgGa 2 O 4, ZnGa 2 O 4, MgIn 2 O 4, CaIn 2 O 4, FeIn 2 O 4, CoIn 2 O 4 , NiIn ₂ O _4, CdIn may be at least one selected from ₂ O _{4, and} the group consisting of _HgIn2 O _4.

For example, the oxide may be at least one selected from the group consisting of SnMg ₂ O ₄ , SnZn ₂ O ₄ , MgAl ₂ O ₄ , CuAl ₂ O ₄ , ZnAl ₂ O _4, and NiAl ₂ O ₄ .

For example, the oxide may be at least one selected from the group consisting of SnMg ₂ O ₄ , SnZn ₂ O _4, and MgAl ₂ O ₄ .

 The lithium-free oxide may have I (440) / I (311) of 0.3 or more, which is the ratio of the peak intensity of the (440) crystal face to the peak intensity of the (311) crystal face in the X-ray diffraction spectrum. For example, I (440) / I (311) may be 0.3 to 0.7.

The lithium-free oxide may have I (511) / I (311) of 0.25 or more, which is the ratio of the peak intensity of the (511) crystal face to the peak intensity of the (311) crystal face in the X-ray diffraction spectrum. For example, I (511) / I (311) may be 0.25 to 0.5.

The lithium-free oxide may have I (511) / I (440) of 0.5 or more, which is the ratio of the peak intensity of the (511) crystal face to the peak intensity of the (440) crystal face in the X-ray diffraction spectrum. For example, I (511) / I (440) may be 0.5 to 0.9.

The content of the lithium-free oxide may be 10% by weight or less, for example, 5% by weight or less based on the total weight of the electrode active material. For example, the content of the lithium-free oxide may be more than 0 to 10% by weight. For example, the content of the lithium-free oxide may be more than 0 to 5% by weight.

In the electrode active material, the surface treatment layer may include at least two elements selected from the group consisting of a metal having a mass of 9 or more and a quasi metal. The element may be at least one selected from the group consisting of Sn, Mg, Mo, Cu, Zn, Ti, , V, Mn, Ga, Fe, Cr, Rh, In, Pb, Co, Ge, Cd, Hg, Sr, W and Be.

The content of the at least two elements selected from the group consisting of a metal having a weight of 9 or more and a metalloid included in the surface treatment layer may be 10% by weight or less, for example, 0 to 6% by weight based on the total weight of the electrode active material.

In the surface treatment layer, a composition ratio of at least two elements selected from the group consisting of a metal having a oxygen to atomic weight of 9 or more and a metalloid metal may be 4: 2.1 to 3.9. For example, the composition ratio may be 4: 2.5 to 3.5. For example, the composition ratio may be 4: 2.9 to 3.1. For example, the composition ratio may be 4: 3. The composition ratio corresponds to a composition ratio of oxygen to A + B in a lithium-free oxide having a composition formula of AB ₂ O ₄ contained in the surface treatment layer.

In the electrode active material, the thickness of the surface treatment layer may be 1 to 1 占 퐉. For example, the thickness of the surface treatment layer may be 1 nm to 1 占 퐉. For example, the thickness of the surface treatment layer may be 1 nm to 100 nm. For example, the thickness of the surface treatment layer may be 1 nm to 30 nm.

The surface treatment layer on the electrode active material may completely cover the core, or may be partially formed on the core in an island type.

In the electrode active material, the core may be particles having an average particle diameter of 10 nm to 50 μm. For example, the average particle diameter of the core may be 10 nm to 30 占 퐉. For example, the average particle size of the core may be 1 탆 to 30 탆.

The core capable of intercalating and deintercalating lithium in the electrode active material may include a cathode active material. The cathode active material may be a lithium transition metal oxide. The lithium transition metal oxide can be used for the positive electrode of a lithium battery, and any lithium metal can be used as long as it can be used in the related art. For example, the lithium transition metal oxide may have a spinel structure or a layered structure.

The lithium transition metal oxide may be a single composition and may be a complex of a compound having a composition of two or more. For example, it may be a complex of compounds having two or more layered structures. Further, it may be a complex of a compound having a layered structure and a compound having a spinel structure.

For example, the lithium transition metal oxide may comprise an excess of overlied oxide (OLO) or a lithium transition metal oxide having an average operating potential of 4.3 V or higher. For example, the average operating potential of the lithium transition metal oxide may be 4.3 to 5.0 V.

The average operation potential means a value obtained by dividing the charge / discharge power amount when the battery is charged / discharged at the upper and lower limits of the charge / discharge potential within the recommended operating voltage range of the battery, by the charge / discharge electricity amount.

The core may include, for example, a compound represented by the following general formulas (1) and (2).

≪ Formula 1 >

Li [Li _a Me _1-a ] O _{2 + d}

(2)

Li [Li _b Me _c M _e ] O _{2 + d}

Wherein 0 < a < 1, b + c + e = 1; 0 < b < 1, 0 < e <0.1; Me is at least one metal selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr and B, , Ir, Ni, and Mg. For example, 0 &lt; a < 0.33.

In addition, the core may comprise a compound represented by the following formulas (3) to (7):

(3)

Li _x Co _1-y M _y O _{2 -?} X _?

&Lt; Formula 4 >

Li _x Co _{1- y z} Ni _y M _z O _{2 - α} X _α

&Lt; Formula 5 >

Li _x Mn _2-y M _y O _{4 -?} X _?

(6)

Li _x Co _2-y M _y O _{4 -?} X _?

&Lt; Formula 7 >

Li _x Me _y M _z PO _{4 -?} X _?

Wherein Me is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, and Ni, where 0? Y? 0.9, 0? Z? 0.5, 1-yz> 0, M, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Ni, Mn, and at least one metal selected from the group consisting of Cu, Al, Cr, Fe, Mg, Sr, V, or a rare earth element, and X is an element selected from the group consisting of O, F, S and P.

In addition, the core may contain a compound represented by the following general formulas (8) to (9).

(8)

pLi ₂ MO ₃ - (1-p) LiMeO ₂

&Lt; Formula 9 >

xLi ₂ MO ₃ -yLiMeO ₂ -zLi _{1 + d} M ' _2-d O ₄

In the above equations, 0 < p < 1, x + y + z = 1; 0 <x <1, 0 <y <1, 0 <z <1; 0? D? 0.33,

Wherein M is at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ti, Zr, Nb, Mo, W, Zn, Al, Si, Ni, Mn, Cr, Fe, Wherein M is at least one metal selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Mg, Zr and B, And at least one metal selected from the group consisting of Mn, Fe, Co, Ni, Cu, Al, Mg,

The compound of Formula 8 has a layered structure. In the compound of Formula 9, Li ₂ MO ₃ -LiMeO ₂ has a layered structure, and Li _{1 + d} M ' _{2 -d} O ₄ has a spinel structure.

The core capable of charging and discharging lithium in the electrode active material may include a negative electrode active material. The negative electrode active material may include at least one selected from the group consisting of a lithium metal, a lithium-alloyable metal, a transition metal oxide, a non-transition metal oxide, and a carbon-based material. The negative electrode active material may be any material that can be used as a negative electrode active material of a lithium battery in the related art.

For example, the metal that can be alloyed with lithium is at least one element selected from the group consisting of Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloys (Y is at least one element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, (Wherein Y is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination element thereof, and not a Sn element) ) And the like. The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Se, Te, Po, or a combination thereof.

For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, or the like.

For example, the non-transition metal oxide may be SnO ₂ , SiO _x (0 <x <2), or the like.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake, spherical or fibrous shape, and the amorphous carbon may be soft carbon or hard carbon carbon, mesophase pitch carbide, calcined coke, and the like.

In the electrode active material, the surface treatment layer may be formed on the core surface by mixing a precursor of a lithium-free oxide having a spinel structure with the core and applying mechanical energy by a dry method.

The electrode according to another embodiment may include the above-described electrode active material. The electrode may be a cathode or a cathode.

The positive electrode may be prepared as follows.

A cathode active material composition is prepared by mixing a cathode active material, a conductive agent, a binder, and a solvent in which a surface treatment layer containing a lithium-free oxide having a spinel structure is formed on at least a part of its surface. The positive electrode active material composition is directly coated on the aluminum current collector and dried to produce a positive electrode plate having a positive electrode active material layer. Alternatively, the cathode active material composition may be cast on a separate support, and then a film obtained by peeling the support from the support may be laminated on the aluminum current collector to produce a cathode plate having a cathode active material layer.

Examples of the conductive agent include carbon black, graphite fine particle natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fiber; Metal powders or metal fibers or metal tubes such as carbon nanotubes, copper, nickel, aluminum, and silver; Conductive polymers such as polyphenylene derivatives, and the like may be used, but the present invention is not limited thereto, and any conductive material may be used as the conductive material in the related art.

Examples of the binder include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), a mixture of the above-mentioned polymers, a styrene butadiene rubber- Polymer, etc. may be used. As the solvent, N-methylpyrrolidone (NMP), acetone, water and the like may be used, but not limited thereto, and any of them can be used in the technical field. The content of the cathode active material, the conductive agent, the binder, and the solvent is a level commonly used in a lithium battery.

The negative electrode may be manufactured in the same manner as the positive electrode except that the negative electrode active material is used instead of the positive electrode active material.

For example, the cathode may be prepared as follows.

A negative electrode active material composition is prepared by mixing a negative electrode active material, a conductive agent, a binder and a solvent in which a surface treatment layer containing a lithium-free oxide having a spinel structure is formed on at least a part of the surface, The negative electrode plate can be manufactured by directly coating the copper collector. Alternatively, the negative electrode active material composition may be cast on a separate support, and the negative electrode active material film peeled from the support may be laminated on a copper current collector to produce a negative electrode plate.

As the conductive agent, binder and solvent in the negative electrode active material composition, the same materials as those of the positive electrode may be used. In some cases, a plasticizer may be further added to the cathode active material composition and the anode active material composition to form pores inside the electrode plate.

The content of the negative electrode active material, the conductive agent, the binder and the solvent is a level commonly used in a lithium battery. Depending on the application and configuration of the lithium battery, one or more of the conductive material, the binder, and the solvent may be omitted.

A lithium battery according to another embodiment employs the electrode. The lithium battery can be manufactured, for example, as follows.

First, a positive electrode and a negative electrode according to one embodiment are manufactured as described above. And an electrode active material on which at least one of the positive electrode and the negative electrode has a surface treatment layer formed on a core capable of lithium intercalation and deintercalation, the surface treatment layer having a spinel structure and containing a lithium-free oxide excluded from the impurity phase.

Next, a separator to be inserted between the positive electrode and the negative electrode is prepared. The separator is usable as long as it is commonly used in a lithium battery. A material having low resistance against the ion movement of the electrolyte and excellent in the ability to impregnate the electrolyte may be used. For example, selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be nonwoven fabric or woven fabric. For example, a rewindable separator such as polyethylene, polypropylene, or the like is used for the lithium ion battery, and a separator having excellent organic electrolyte impregnation capability can be used for the lithium ion polymer battery. For example, the separator may be produced according to the following method.

A polymer resin, a filler and a solvent are mixed to prepare a separator composition. The separator composition may be coated directly on the electrode and dried to form a separator. Alternatively, after the separator composition is cast and dried on a support, a separator film peeled from the support may be laminated on the electrode to form a separator.

The polymer resin used in the production of the separator is not particularly limited, and any material used for the binder of the electrode plate may be used. For example, vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate or mixtures thereof may be used.

Next, the electrolyte is prepared.

For example, the electrolyte may be an organic electrolyte. In addition, the electrolyte may be a solid. For example, boron oxide, lithium oxynitride, and the like, but not limited thereto, and any of them can be used as long as they can be used as solid electrolytes in the art. The solid electrolyte may be formed on the cathode by a method such as sputtering.

For example, an organic electrolytic solution can be prepared. The organic electrolytic solution can be prepared by dissolving a lithium salt in an organic solvent.

The organic solvent may be any organic solvent which can be used in the art. Examples of the solvent include propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate , N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, tetrahydrofuran, tetrahydrofuran, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, , Dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether or mixtures thereof.

The lithium salt may also be used as long as it can be used in the art as a lithium salt. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiCl, LiI, or a mixture thereof.

As shown in FIG. 6, the lithium battery 1 includes an anode 3, a cathode 2, and a separator 4. The anode 3, the cathode 2 and the separator 4 described above are wound or folded and housed in the battery case 5. Then, an organic electrolytic solution is injected into the battery case 5 and is sealed with a cap assembly 6 to complete the lithium battery 1. The battery case may have a cylindrical shape, a rectangular shape, a thin film shape, or the like. For example, the lithium battery may be a large-sized thin-film battery. The lithium battery may be a lithium ion battery.

A separator may be disposed between the anode and the cathode to form a battery structure. The cell structure is laminated in a bi-cell structure, then impregnated with an organic electrolyte solution, and the obtained result is received in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of battery assemblies may be stacked to form a battery pack, and such battery pack may be used for all devices requiring high capacity and high output. For example, a notebook, a smart phone, an electric vehicle, and the like.

Further, the lithium battery has excellent storage stability, lifetime characteristics and high-rate characteristics at high temperatures, and thus can be used in an electric vehicle (EV). For example, a hybrid vehicle such as a plug-in hybrid electric vehicle (PHEV).

According to another embodiment of the present invention, there is provided a method of manufacturing an electrode active material, comprising: mixing a core containing an electrode active material and a lithium-free oxide particle having a spinel structure; And forming a surface treatment layer containing a lithium-free oxide on the core by a dry method.

The dry method includes both a method of forming a surface treatment layer by applying mechanical energy to a mixture of a core containing an electrode active material and a lithium-free oxide particle having a spinel structure without using a solvent.

The dry method comprises the steps of: a) bringing the powder of a coating material, for example, a lithium-free oxide having a spinel structure, into contact with the surface of the core particle with a low rotation ball mill or the like, B) a method of restraining the covering material particles on the surface of the core particles by the action of a pulverizing medium or a rotor in the apparatus to bond the core and the covering material particles to each other and at the same time, A method of mechanically bonding the covering material particles on the core particle with each other or softening or melting the surface treatment layer of the covering material particles on the core particle by heat generated from the stress to bond these particles, The surface treatment layer formed and a part or all of the surface treatment layer and the core And then cooling again. However, the present invention is not limited to these methods, and all of the dry methods that can be used in the art can be used.

For example, the drying method may be one selected from the group consisting of a planetary ball mill method, a low speed ball mill method, a high speed ball mill method, a hybridization method, and a mechanofusion method. For example, a mechanofusion method can be used. In the mechanofusion method, the mixture is charged into a rotating container, and the mixture is fixed to the inner wall of the container by centrifugal force, and then compressed into a gap between the inner wall of the container and an adjacent arm head at a slight interval. The mechanofusion method corresponds to the method b) above.

The method may further include the step of heat treating the resultant having the surface treatment layer formed after the surface treatment layer is formed by the dry method. The surface treatment layer can be further strengthened by the heat treatment. The heat treatment condition may be any condition as long as a part or all of the surface treatment layer can be melted.

In the above production process, the content of the lithium-free oxide may be 10% by weight or less of the total weight of the core and the lithium-free oxide. For example, the content of the lithium-free oxide may be 5 wt% or less of the total weight of the core and the lithium-free oxide. For example, the content may be from greater than 0 to 10% by weight. For example, the content may be greater than 0 and 5 wt%.

In the above manufacturing method, the production of the lithium-free oxide particles includes: preparing a mixture by milling a lithium-free oxide precursor; And firing the mixture to prepare a lithium-free oxide having a spinel structure.

In the step of preparing the mixture by milling the lithium-free oxide precursor, the lithium-free oxide precursor may be treated with a ball mill or the like to preliminarily react the precursor particles to form an intermediate phase. The intermediate phase may be an oxide comprising an oxide comprising two or more transition metals.

By including the intermediate phase in the mixture, various secondary phase formation due to the volatilization of ZnO in the baking step, that is, the formation of an impurity phase, can be prevented. That is, a lithium-free oxide having a spinel structure in which the impurity phase is removed in spite of high-temperature firing in the firing step due to the formation of the intermediate phase can be produced. In addition, the crystallinity of the lithium-free oxide can be improved by the high temperature calcination.

The method may further include a step of grinding the lithium-free oxide after the step of preparing the lithium-free oxide having the spinel structure. By the pulverizing step, lithium-free oxide nanoparticles can be prepared. The nanoparticles may have a particle diameter of 10 nm to 1000 nm.

The calcination of the mixture can be carried out at a high temperature of 700 to 1500 ° C. For example, the firing can be performed at 1000 to 1400 ° C.

The firing of the mixture is performed at a high temperature, so that the physical properties of the surface treatment material can be more easily controlled. For example, since the firing temperature can be easily controlled, the content of impurities and the like can be more easily controlled. On the other hand, when the mixture is heat-treated at the same time as the core, it is difficult to control the physical properties of the surface-treated material because the firing temperature is limited to a low temperature of less than 700 ° C to prevent deterioration of the core.

In the above manufacturing method, the firing may be performed for 12 to 72 hours. For example, the calcination may be carried out for 24 to 60 hours. For example, the calcination may be carried out for 36 to 60 hours.

The calcination may be carried out in an oxygen, air and nitrogen atmosphere. For example, the firing may be performed in an air atmosphere.

The present invention will be described in more detail by way of the following examples and comparative examples. However, the examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

(Preparation of lithium-free oxide having spinel structure)

Production Example 1 (dry method)

SnO (tin oxide) and ZnO (zinc oxide) were mixed at a composition ratio of 1: 2 and then milled in a planetary ball mill (Fritsch, Planetary mono mill 6) at 300 to 500 rpm for 5 hours. Subsequently, the resultant was fired at 1200 ° C. for 48 hours in an air atmosphere to prepare SnZn ₂ O ₄ having a spinel structure. Then, the SnZn ₂ O ₄ was pulverized with a paint shaker for 1 hour to prepare SnZn ₂ O ₄ nanoparticles having a particle size of about 100 nm.

An SEM photograph of the SnZn ₂ O ₄ nanoparticles prepared in Preparation Example 1 is shown in FIG.

Comparative Preparation Example 1 (co-precipitation method)

A first aqueous solution was prepared by adding SnCl ₄ (tin chloride) and Zn (NO ₃ ) ₂ (zinc nitrate) to water at a composition ratio of 1: 2. A second aqueous solution was prepared by adding LiOH to water. The first aqueous solution and the second aqueous solution were mixed to coprecipitate SnZn ₂ (OH) ₈ . The precipitated SnZn ₂ (OH) ₈ was filtered and dried, and then fired in an oxygen atmosphere at 850 ° C for 12 hours in an oxygen atmosphere to prepare SnZn ₂ O ₄ . Then, the SnZn ₂ O ₄ was pulverized with a paint shaker for 1 hour to prepare SnZn ₂ O ₄ nanoparticles having a particle size of about 100 nm.

(Preparation of surface-treated 5 V cathode active material)

Example 1

SnO (tin oxide) and ZnO (zinc oxide) were mixed at a composition ratio of 1: 2 and then milled in a planetary ball mill (Fritsch, Planetary mono mill 6) at 300 to 500 rpm for 5 hours. Subsequently, the resultant was fired at 1200 ° C. for 48 hours in an air atmosphere to prepare SnZn ₂ O ₄ having a spinel structure. Then, the SnZn ₂ O ₄ was pulverized with a paint shaker for 1 hour to prepare SnZn ₂ O ₄ nanoparticles having a particle size of about 100 nm.

3 parts by weight of the SnZn ₂ O ₄ nanoparticles and 97 parts by weight of LiNi _0.5 Mn _1.5 O ₄ powder having an average particle size of 10 μm were mixed. 3 shows a LiNi _0.5 Mn _1.5 O ₄ powder having an average particle size of 10 mu m. The mixture was placed in a dry surface treatment apparatus (Hosokawa Micron Corporation, Japan, Mechanofusion device, Nobilta-130) and treated at 6000 rpm for 5 minutes to form a surface treatment layer containing SnMg ₂ O ₄ on the LiNi _0.5 Mn _1.5 O ₄ core Thereby preparing a cathode active material. The prepared positive electrode active material is shown in Fig.

Example 2

A cathode active material was prepared in the same manner as in Example 1, except that SnM (tin oxide) and MgO (magnesium oxide) were used as a lithium-free oxide precursor and a surface treatment layer containing SnMg ₂ O ₄ was formed on the surface. Respectively.

Example 3

Example 1 was repeated except that magnesium oxide (MgO) and aluminum oxide (Al ₂ O ₃ ) were used as a lithium-free oxide precursor and a surface treatment layer containing MgAl ₂ O ₄ was formed on the surface thereof by controlling the composition ratio. The cathode active material was prepared in the same manner.

Example 4

Example 1 was repeated except that CuO (copper oxide) and Al ₂ O ₃ (aluminum oxide) were used as a lithium-free oxide precursor and a surface treatment layer containing CuAl ₂ O ₄ was formed on the surface by controlling the composition ratio. The cathode active material was prepared in the same manner.

Example 5

Example 1 was repeated except that ZnO (zinc oxide) and Al ₂ O ₃ (aluminum oxide) were used as the lithium-free oxide precursor and the surface treatment layer containing ZnAl ₂ O ₄ was formed on the surface by controlling the composition ratio. The cathode active material was prepared in the same manner.

Example 6

Example 1 was repeated except that NiO (Al ₂ O ₃ ) and Al ₂ O ₃ (Al ₂ O ₃ ) were used as a lithium-free oxide precursor and a surface treatment layer containing NiAl ₂ O ₄ was formed on the surface by controlling the composition ratio. The cathode active material was prepared in the same manner.

Examples 7-12

Except that the amount of the oxide precursor used was changed to 1 wt% (a mixture of 1 part by weight of the lithium-free oxide and 99 parts by weight of the positive electrode active material) Respectively.

Examples 13 to 18

Except that the amount of the oxide precursor used was changed to 5 wt% (a mixture of 5 parts by weight of the lithium-free oxide and 95 parts by weight of the positive electrode active material) Respectively.

Examples 19 to 24

Except that the amount of the oxide precursor used was changed to 10 wt% (a mixture of 10 parts by weight of the lithium-free oxide and 90 parts by weight of the positive electrode active material) Respectively.

Comparative Example 1

LiNi _0.5 Mn _1.5 O ₄ having an average particle size of 15 μm was used as a cathode active material without any surface treatment layer production process.

(Preparation of surface-treated OLO cathode active material)

Example 25

SnO (tin oxide) and ZnO (zinc oxide) were mixed at a composition ratio of 1: 2 and then milled in a planetary ball mill (Fritsch, Planetary mono mill 6) at 300 to 500 rpm for 5 hours. Subsequently, the resultant was fired at 1200 ° C. for 48 hours in an air atmosphere to prepare SnZn ₂ O ₄ having a spinel structure. Then, the SnZn ₂ O ₄ was pulverized with a paint shaker for 1 hour to prepare SnZn ₂ O ₄ nanoparticles having a particle size of about 100 nm.

3 parts by weight of the SnZn ₂ O ₄ nanoparticles and 97 parts by weight of Li [Li _0.05 Ni _0.45 Co _0.16 Mn _0.35 ] O ₂ powder having an average particle size of 10 μm were mixed. Dry surface treatment apparatus and the mixture containing the (Hosokawa Micron Corporation, Japan, Mechanofusion device, Nobilta-130) placed for 5 minutes 6000rpm processing by _{Li [Li 0.05 Ni 0.45 Co 0.16} Mn 0.35] O 2 SnZn on the core ₂ O ₄ To prepare a positive electrode active material having a surface-treated layer.

Example 26

Except that SnM (tin oxide) and MgO (magnesium oxide) were used as a lithium-free oxide precursor and a surface treatment layer containing SnMg ₂ O ₄ was formed on the surface thereof. Respectively.

Example 27

Example 25 was repeated except that magnesium oxide (MgO) and aluminum oxide (Al ₂ O ₃ ) were used as a lithium-free oxide precursor and a surface treatment layer containing MgAl ₂ O ₄ was formed on the surface thereof by controlling the composition ratio. The cathode active material was prepared in the same manner.

Example 28

Example 25 was repeated except that CuO (copper oxide) and Al ₂ O ₃ (aluminum oxide) were used as the lithium-free oxide precursor and the surface treatment layer containing CuAl ₂ O ₄ was formed on the surface by controlling the composition ratio. The cathode active material was prepared in the same manner.

Example 29

Except that ZnO (aluminum oxide) and Al ₂ O ₃ (aluminum oxide) were used as a lithium-free oxide precursor and the surface treatment layer containing ZnAl ₂ O ₄ was formed on the surface by controlling the composition ratio. The cathode active material was prepared in the same manner.

Example 30

Example 25 was repeated except that NiO (Al ₂ O ₃ ) and Al ₂ O ₃ (aluminum oxide) were used as the lithium-free oxide precursor and the surface treatment layer containing NiAl ₂ O ₄ was formed on the surface thereof by controlling the composition ratio. The cathode active material was prepared in the same manner.

Examples 31 to 36

The surface treatment layer was formed in the same manner as in Examples 25 to 30 except that the content of the lithium-free oxide used was changed to 1 wt% (a mixture of 1 part by weight of the lithium-free oxide and 99 parts by weight of the positive electrode active material) And the resulting positive electrode active material was prepared.

Examples 37 to 42

Except that the content of the lithium-free oxide used was changed to 5 wt% (a mixture of 5 parts by weight of the lithium-free oxide and 95 parts by weight of the positive electrode active material) And the resulting positive electrode active material was prepared.

Examples 43 to 48

The surface treatment layer was formed in the same manner as in Examples 25 to 30 except that the content of the lithium-free oxide used was changed to 10 wt% (a mixture of 10 parts by weight of the lithium-free oxide and 90 parts by weight of the positive electrode active material) And the resulting positive electrode active material was prepared.

Comparative Example 2

Li [Li _0.05 Ni _0.45 Co _0.16 Mn _0.35 ] O ₂ having an average particle size of 10 [mu] m was used as the cathode active material without any surface treatment layer preparation process.

(Preparation of positive electrode)

Example 49

(Ketchen Black, EC-600 JD) and polyvinylidene fluoride (PVdF) in a weight ratio of 93: 3: 4 prepared in Example 1 was dissolved in N-methylpyrrolidone NMP) were mixed in agate mortar to prepare a slurry. The slurry was coated on an aluminum current collector having a thickness of 15 탆 using a doctor blade to a thickness of about 20 탆, dried at room temperature, and dried again under vacuum at 120 캜 to prepare a positive electrode plate having a positive electrode active material layer.

Examples 50 to 96

A positive electrode plate was prepared in the same manner as in Example 49 except that each of the positive electrode active materials of Examples 2 to 48 was used.

Comparative Examples 3 to 4

A positive electrode plate was prepared in the same manner as in Example 49 except that the positive electrode active materials of Comparative Examples 1 and 2 were respectively used.

(Production of lithium battery)

Example 97

Using the positive electrode plate prepared in Example 49, lithium metal was used as a counter electrode, and a PTFE separator and 1.3M LiPF ₆ were added to EC (ethylene carbonate) + DEC (diethyl carbonate) (3: 7 volume ratio) A coin cell was prepared using the dissolved solution as an electrolyte.

Examples 98 to 144

Were prepared in the same manner as in Example 97, except that the positive electrodes prepared in Examples 50 to 96 were used, respectively.

Comparative Examples 5 to 6

Were prepared in the same manner as in Example 97, except that the positive electrodes prepared in Comparative Examples 3 to 4 were used, respectively.

Evaluation example 1: XRD experiment

XRD (X-ray diffraction) experiments were performed on the surfaces of SnZn ₂ O ₄ prepared in Preparation Example 1 and Comparative Preparation Example 1, and the results are shown in FIG. XRD was measured using a Cu-K? Line.

1 (a) shows XRD results for SnZn ₂ O ₄ prepared in Comparative Production Example 1. FIG.

1 (b) shows the XRD results for the SnZn ₂ O ₄ prepared in Preparation Example 1.

As also shown in the Production Example 1 as shown in 1 (a) SnZn ₂ O ₄ is I've found this characteristic peaks only for SnZn ₂ O ₄ having a spinel structure, and Fig. 1 (b) Comparative SnZn2O4 of Production Example 1 showed a large peak corresponding to an impurity phase. The SnZn ₂ O ₄ produced in Production Example 1 contained substantially no impurities. That is, in the X-ray diffraction spectrum using the Cu-K? Line, the intensity of the peak with respect to the impurity was below the noise level.

In FIG. 1 (a), a diffraction peak with respect to the (311) plane was observed in the vicinity of 2? = 34 占 and the half-value width FWHM of the diffraction peak was 0.530 占. In contrast, in FIG. 1 (b), the half-value width FWHM of the diffraction peak with respect to the (311) plane was 0.260 °. That is, SnZn ₂ O of preparation ₁₄ was significantly improved crystallinity compared with the Comparative Preparation Example 1 of the SnZn ₂ O _4.

Evaluation Example 2: ICP experiment

An ICP (Ion Coupled Plasma) test was performed on the surface of the cathode active material prepared in Example 1 above.

The instrument used for the ICP experiment was Shimadzu ICPS-8100. The Sn: Zn composition ratio on the surface of the positive electrode active material was 1.000: 2.000.

Evaluation Example 3: High temperature stability test at 60 캜

The coin cells prepared in Examples 97 to 120 and Comparative Example 5 were charged at a constant current of 4.45 V at a rate of 0.05 C in the 1st cycle and discharged at a constant current of 3.0 V at a rate of 0.05C. The 2 ^nd cycle was charged to 4.45 V at a rate of 0.1 C, then charged at a constant voltage until the current became 0.05 C while maintaining the voltage at 4.45 V, and discharged at a rate of 0.1 C at a constant current of 3.0 V. The 3 ^rd cycle was charged to 4.45 V at a rate of 0.5 C and then charged at 4.45 V until the current reached 0.05 C, and discharged at a rate of 0.2 C at a constant current of 3.0 V. The discharge capacity in the 3 ^rd cycle was regarded as a standard capacity.

The battery was charged to 4.45 V at a speed of 0.5 C in the fourth cycle and was then charged at a constant voltage until the current became 0.05 C while being maintained at 4.45 V. The charged battery was stored in an oven at 60 캜 for 7 days, And discharged at a rate of 0.1 C to 3.0 V at a rate of 4 th cycle. Part of the charge and discharge results are shown in Table 1 below. The capacity retention after storage at high temperature is defined by the following equation (1).

&Quot; (1) &quot;

Capacity retention rate after storage at high temperature [%] = [discharge capacity after leaving at high temperature for 4th cycle / standard capacity] × 100

(The standard capacity is the discharge capacity in 3 ^rd cycles)

Evaluation Example 4: High temperature stability test at 90 캜

The coin cells prepared in Examples 97 to 120 and Comparative Example 5 were tested in the same manner as in Evaluation Example 3 except that the packed cells were stored in a 90 ° C oven for 4 hours. Part of the charge and discharge results are shown in Table 1 below. The capacity retention after storage at high temperature is defined by Equation (1).

After maintaining for 7 days at 60 ℃, capacity maintenance rate [%] After maintaining at 90 ℃ for 4 hours Capacity retention rate [%] Comparative Example 5 1.7 58.2 Example 97 43.7 77.7 Example 98 41.6 75.6

As shown in Table 1, the lithium battery of Examples 97 to 98 exhibited remarkably improved capacity retention after storage at a high temperature compared with the lithium battery of Comparative Example 5. [ That is, the high temperature stability was remarkably improved.

Evaluation Example 7: High temperature charge / discharge test

The coin cells prepared in Examples 97 to 120 and 5 were charged and discharged 100 times at a constant current of 1 C rate in a voltage range of 3.5 to 4.9 V relative to lithium metal at a high temperature of 60 ° C. The capacity retention rate in the 100th cycle is expressed by the following equation (2). The initial coulomb efficiency is expressed by the following equation (3). The capacity retention rate and the initial coulombic efficiency in the 100th cycle are shown in Table 2 below.

&Quot; (2) &quot;

Capacity retention rate in 100 ^th cycle [%] = [Discharge capacity in 100th cycle / Discharge capacity in 1 ^th cycle] × 100

&Quot; (3) &quot;

Initial coulomb efficiency [%] = [discharge capacity in 1st cycle / charge capacity in 1 ^th cycle] × 100

Capacity retention rate in 100 ^th cycle
[%] Early coulomb efficiency
[%] Comparative Example 5 74.4 89.5 Example 97 81.8 93.8 Example 98 83.1 94.4

As shown in Table 2, the lithium batteries of Examples 97 to 98 exhibited improved high-temperature lifetime characteristics and initial coulone efficiency as compared with the lithium battery of Comparative Example 5.

Evaluation Example 6: High Rate Characteristic Experiment

The coin cells prepared in Examples 97 to 98 and Comparative Example 5 were charged at a constant current of 0.1 C rate in a voltage range of 3.5 to 4.9 V relative to lithium metal at room temperature while maintaining the capacity maintenance rate Is shown in Fig. The current densities at discharge were 0.1 C, 0.2 C, 0.5 C, 1 C, 2 C, 5 C, 8 C and 10 C rates, respectively. 5, the capacity retention rate is calculated from the following equation (4).

&Quot; (4) &quot;

Percentage of Capacity Retention Rate [%] = [Discharge Capacity per Rate / Discharge Capacity at 0.1C] x 100

As shown in FIG. 5, the lithium batteries of Examples 97 to 98 have improved high-rate characteristics as compared with the lithium batteries of Comparative Example 5.

Claims (6)

Mixing a core comprising an electrode active material with lithium-free oxide particles having a spinel structure; And
And forming a surface treatment layer containing a lithium-free oxide on the core by a dry method. The method according to claim 1, wherein the drying method is one selected from the group consisting of a ball mill method, a low speed ball mill method, a high speed ball mill method, a hybridization method, and a mechanofusion method . The method according to claim 1, further comprising the step of heat treating the resultant having the surface treatment layer formed after the step of forming the surface treatment layer by the dry method. The process according to claim 1, wherein the content of the lithium-free oxide is 10 wt% or less of the total weight of the mixture. The method of claim 1, wherein the preparation of the lithium-free oxide particles comprises:
Milling the lithium-free oxide precursor to prepare a mixture; And
And firing the mixture to prepare a fired product. 6. The method according to claim 5, wherein the calcination is performed at 700 to 1500 DEG C for 12 to 72 hours.

Images