KR20180102874A - Nickel-based cathode material and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a nickel-based positive electrode material and a method of manufacturing the same, and more specifically, to a manufacturing method of a Ni-rich positive electrode material having excellent physical and chemical properties using an effective and simple process; and to the Ni-rich positive electrode material manufactured through the method.

Description

[0001] The present invention relates to a nickel-based cathode material and a method for manufacturing the same,

The present invention relates to a nickel-based cathode material and a method of manufacturing the same, and more particularly, to a nickel-based cathode material having an electrochemical performance with a significantly improved rate capability and cycling stability, and a method of manufacturing the same.

The anode of a lithium rechargeable battery is typically a powdered material capable of reversibly inserting and desorbing lithium. The powder is deposited as an electrode film on a metal foil serving as a current collector. The electrode film often contains more than 95% of the cathode material and a small amount of binder and conductive additive. The anode (cathode) thus produced is laminated or wound on the separator and the cathode film (anode). Generally, the cathode film contains carbon. Finally, the stacked or wound cathode-separator-anode-roll is inserted into the case, the electrolyte is added, and the case is sealed to form a complete cell.

Conventionally, LiCoO ₂ has been a leading cathode material in rechargeable lithium batteries. In recent years, so-called NCM cathode materials have replaced LiCoO ₂ in many applications. "NCM" is an abbreviation for nickel-cobalt-manganese and is used for a lithium transition metal oxide wherein the transition metal is essentially a mixture of Ni, Co and Mn and has approximately stoichiometric LiMO _{2 wherein} M = Ni _x Mn _y Co _z . Further doping is possible. Typical doping elements are Al, Mg, Zr, and the like. The crystal structure has an ordered salt structure, in which cations are arranged in two-dimensional Li and M layers. The space group is R-3M. There are a number of different compositions as possible compositions, which are often classified and named according to their nickel, manganese and cobalt content. Typical NCM-based material is _{"111" (Ni 1/3} Co 1/3 Mn 1/3), "523" (Ni 0. 5 Co 0. 2 Mn 0 .3), "622" (Ni 0.6 Co 0.2 Mn _0.2 ).

The nickel excess in the composition of NCM is an important stoichiometric parameter. As the nickel content increases, the reversible capacity increases, but at the same time, the cathode material becomes increasingly difficult to manufacture. &Quot; 111 " (Ni _1/3 Co _1/3 Mn _1/3 ) in which the excess amount of Ni = 0 is used in combination with the inexpensive Li ₂ CO ₃ as a lithium source, Material.

_{"811" (Ni 0. 8} Mn 0. 1 Co 0. 1) Ni-rich designed as a cathode material Ni-rich LNMCO such as _{(. LiNi 0 8 Co 0.} 1 Mn 0. 1 O 2) is reversible capacity (reversible capacity) is large and is very attractive as a cathode material. However, the Ni-rich cathode material has low electrochemical performance and low electrochemical performance because of low diffusion rate of Li ^{+ in} the structure.

In particular, it becomes highly delithiated at a high voltage of 4.3V or higher, which exhibits severe capacity discoloration. In order to solve these problems, there are many methods of surface modification of Ni-rich cathode materials using CeO ₂ , ZnO and TiO ₂ and realization of core-shell structure or concentration-gradient structure of Ni-rich cathode materials Efforts have been made. However, some of these workarounds are costly because they involve complex processes.

In addition, the Ni-rich cathode material is not easily oxidized from Ni ^{2 +} to Ni ^{3 +} even in a pure oxygen atmosphere. Therefore, in order to obtain a high-performance Ni-rich cathode material, it is generally calcined in a pure oxygen atmosphere. This is more expensive than calcining Ni-rich cathode materials in air.

The poor cycling stability and cost of the Ni-rich cathode material was a serious problem limiting the commercialization of the Ni-rich cathode material. Therefore, it is necessary to study a novel Ni-rich cathode material which overcomes the problems of the Ni-rich cathode material and a manufacturing method thereof.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve the problems and disadvantages of the prior art, and it is an aspect of the present invention to provide a method of manufacturing a Ni-rich LNMCO cathode material.

Another aspect of the present invention is to provide a Ni-rich LNMCO cathode material.

According to an aspect of the present invention, there is provided a method of manufacturing a Ni-rich LNMCO cathode material.

The method for preparing the Ni-rich LNMCO cathode material comprises the steps of preparing a mixed solution having a nickel aqueous solution, a cobalt aqueous solution and a manganese aqueous solution, adding an oxidizing agent to the mixed solution, adding an LNMCO precursor powder Filtering and mixing the LNMCO precursor powder with a source of lithium (Li).

The molar ratio of the nickel aqueous solution, the cobalt aqueous solution and the manganese aqueous solution may be 1-x-y: x: y (0 <x? 0.4, 0 <y? 0.4, 0 <x + y? 0.5).

The nickel aqueous solution, the cobalt aqueous solution and the manganese aqueous solution may be a nickel sulfate aqueous solution (NiSO ₄ .6H ₂ O), a cobalt sulfate aqueous solution (CoSO ₄ .7H ₂ O) and a manganese sulfate aqueous solution (MnSO ₄ .6H ₂ O), respectively.

The oxidizing agent may be potassium permanganate (KMnO ₄ ).

In the step of adding the oxidizing agent to the mixed solution, the amount of the oxidizing agent may be 10 mol% or less relative to the sum of the total moles of the aqueous nickel solution, aqueous solution of cobalt and aqueous solution of manganese.

The formula of the LNMCO precursor powder is Ni _{1 -x- y} Co _x Mn _y (OH) _{2 + z} (0 <x? 0.4, 0 <y? 0.4, 0 <x + y? 0.5, 0 <z <Lt; / RTI &gt;

The valence state of the nickel contained in the LNMCO precursor powder may be a mixed state of Ni ^{2 +} and Ni ^{3 +} .

The lithium (Li) source may be lithium hydroxide.

According to another aspect of the present invention, there is provided a Ni-rich LNMCO cathode material.

The Ni-rich LNMCO cathode material is prepared by the above-described method of producing a Ni-rich LNMCO cathode material.

The Ni-rich LNMCO cathode material may be a layered structure.

According to the present invention, highly oxidized Ni-rich LNMCO cathode materials can be prepared by using pre-oxidized NCM as a precursor of Ni-rich LNMCO cathode material.

In addition, by using NCM pre-oxidized as a precursor of the Ni-rich LNMCO cathode material, a Ni-rich LNMCO cathode material having a more stable layered structure can be produced, and thus Ni-rich LNMCO cathode material Have excellent electrochemical performance.

Also, by using pre-oxidized NCM as a precursor of Ni-rich LNMCO cathode material, Ni-rich LNMCO cathode material with improved rate capabilities can be manufactured.

Also, by using pre-oxidized NCM as a precursor of Ni-rich LNMCO cathode material, it is possible to maintain high capacity retention values in high cut-off voltage cycles above 4.3V Ni-rich LNMCO cathode material can be manufactured.

In addition, by using pre-oxidized NCM as a precursor of Ni-rich LNMCO cathode material, a Ni-rich LNMCO cathode material with a more favorable structure for Li ⁺ intercalation / de-intercalation can be obtained. Can be manufactured.

In addition, by using pre-oxidized NCM as a precursor of Ni-rich LNMCO cathode material, Ni-rich LNMCO cathode material with low degree of cation disorder between Li ⁺ and Ni ²⁺ Can be manufactured.

In addition, Ni-rich LNMCO cathode materials with well-ordered layered structures can be prepared by using pre-oxidized NCM as a precursor of Ni-rich LNMCO cathode material.

Further, by using NCM pre-oxidized with a precursor of the Ni-rich LNMCO cathode material, a battery cell having a higher capacity retention rate can be manufactured.

In addition, pre-oxidation of the precursor of the Ni-rich cathode material is an efficient and simple process from a cost point of view and can provide an excellent Ni-rich cathode material without the conventional sintering process under pure oxygen atmosphere.

The technical effects of the present invention are not limited to those mentioned above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a flow chart showing a preferred method of producing the Ni-rich LNMCO cathode material of the present invention.
2 is an SEM image of the LNMCO precursor powder prepared in Comparative Example 1 of the present invention and Production Example 1 of the present invention.
3 is an XPS spectrum of the LNMCO precursor powder prepared in Comparative Example 1 of the present invention and Production Example 1 of the present invention.
4 is an FTIR graph of the LNMCO precursor powder prepared in Comparative Example 1 of the present invention and Production Example 1 of the present invention.
5 is a SEM image of Ni-rich LNMCO prepared in Comparative Example 2, Comparative Example 3 and Preparation Example 2 of the present invention.
6 is an XRD graph of Ni-rich LNMCO prepared in Comparative Example 2, Comparative Example 3 and Production Example 2 of the present invention.
7 is an XPS spectrum of Ni-rich LNMCO prepared in Comparative Example 2, Comparative Example 3 and Production Example 2 of the present invention.
FIG. 8 is a graph showing charge / discharge characteristics of coin-type cells manufactured using the Ni-rich LNMCO anode materials prepared in Comparative Examples 2, 3, and 2 of the present invention.
FIG. 9 is a graph showing charge / discharge characteristics of coin-type cells manufactured using the Ni-rich LNMCO anode materials prepared in Comparative Examples 2, 3, and 2 of the present invention at higher voltages.
FIG. 10 is a graph showing the discharge capacity ratio (rate capability) according to the charge / discharge rate (C rate) of coin-type cells manufactured using the Ni-rich LNMCO anode materials prepared in Comparative Examples 2, 3, .

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

It will be appreciated that when an element such as a layer, region or substrate is referred to as being present on another element "on," it may be directly on the other element or there may be an intermediate element in between .

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers and / or regions, such elements, components, regions, layers and / And should not be limited by these terms.

Example

1 is a flow chart showing a preferred method of producing the Ni-rich LNMCO cathode material of the present invention.

First, a step of preparing a mixed solution of a nickel aqueous solution, a cobalt aqueous solution and a manganese aqueous solution is performed (S100)

Ni-rich NCM is used as a precursor of the Ni-rich LNMCO cathode material. To obtain the Ni-rich NCM, a mixed solution of nickel aqueous solution, cobalt aqueous solution and manganese aqueous solution is prepared.

 The molar ratio of the nickel solution, the cobalt solution, and the manganese aqueous solution to the mixed solution is in the range of 1: 1 to 1: 1, y? 0.5). Therefore, precursors of all Ni-rich electrode materials having a nickel content of 50% or more and less than 100% can be produced.

Meanwhile, in order to further dope aluminum (Al), a mixed solution may be prepared by further including an aqueous aluminum solution, or a mixed solution may be prepared by including only an aqueous aluminum solution without containing a manganese aqueous solution. In this case, the molar ratio of the nickel aqueous solution, the cobalt aqueous solution, the manganese aqueous solution and the aluminum aqueous solution was set to a molar ratio of nickel aqueous solution: cobalt aqueous solution: manganese aqueous solution = 1-xy: x: ya: a (0 < a < = y, 0 < x + y &lt;

At this time, if the value of a is 0, a mixed solution composed of a nickel aqueous solution, a cobalt aqueous solution and a manganese aqueous solution is prepared. If the a value is y, a mixed solution composed of only nickel aqueous solution, cobalt aqueous solution and aluminum aqueous solution is produced.

Preferred nickel solution according to an embodiment of the present invention, a cobalt solution and a manganese aqueous solution of each of nickel sulfate aqueous solution _{(NiSO 4 · 6H 2 O)} , cobalt sulfate aqueous solution (CoSO ₄ · 7H ₂ O) and manganese sulfate aqueous solution (MnSO ₄ · 6H ₂ O) and a stoichiometric amount corresponding to a molar ratio of NiSO ₄揃 6H ₂ O: CoSO ₄揃 7H ₂ O: MnSO ₄揃 6H ₂ O = 0.8: 0.1: 0.1 was dissolved in deionized water, To obtain a transparent mixed solution.

A nickel solution, a cobalt solution, and a manganese solution is prepared, and then an oxidizing agent is added to the mixed solution (S200).

The Ni-rich NCM used as a precursor of the Ni-rich LNMCO cathode material is pre-oxidized through the addition of the oxidizing agent.

The degree of pre-oxidation of Ni-rich NCM can be controlled by adjusting the amount of the oxidizing agent. The amount of the oxidizing agent is 10 mol% or less relative to the sum of the total moles of the nickel aqueous solution, the aqueous solution of cobalt and the aqueous solution of manganese. Ni-rich NCM can be pre-oxidized if the oxidizing agent is added in a small amount (more than 0 mol%). If the oxidizing agent is used in excess of 10 mol%, a large amount of oxidant precipitation occurs.

The oxidizing agent can be used without limitation as long as it is an oxidizing agent capable of oxidizing the valence of nickel contained in the mixed solution from Ni ^{2 +} to Ni ^{3 +} . Preferably, the oxidizing agent according to an embodiment of the present invention is a strong oxidizing agent potassium permanganate KMnO ₄ ) was used.

After the step of adding the oxidizing agent to the mixed solution, a step of filtering the LNMCO precursor powder in the mixed solution to which the oxidizing agent is added is performed (S300)

The formula of the LNMCO precursor powder is Ni _{1 -x- y} Co _x Mn _y (OH) _{2 + z} (0 <x? 0.4, 0 <y? 0.4, 0 <x + y? 0.5, 0 <z <Lt; / RTI &gt; The values of x and y are determined according to the molar ratio of the aqueous nickel solution, the aqueous solution of cobalt and the aqueous solution of manganese in the step of preparing the mixed solution of the nickel aqueous solution, the cobalt aqueous solution and the manganese aqueous solution.

On the other hand, when a mixed solution is prepared by further containing an aluminum aqueous solution or a mixed solution containing only an aluminum aqueous solution without containing a manganese aqueous solution, Ni _{1 -x- y} Co _x Mn _{y - a} Al _a (OH) _{2 + the} precursor powder having the formula of _z (0 <x? 0.4, 0 <y? 0.4, 0? a? y, 0 <x + y? 0.5, 0 <z <1) is filtered. The values of x, y and a are determined according to the molar ratio of the nickel aqueous solution, the cobalt aqueous solution, the manganese aqueous solution and the aluminum aqueous solution in the step of preparing the nickel aqueous solution, the cobalt aqueous solution, the manganese aqueous solution and the aluminum aqueous solution.

z values and will be determined by the valence states of the respective transition metal ion (Ni, Co and Mn) in the precursor LNMCO, increases in proportion to the fraction of the Ni ^{3 +} to satisfy neutral conditions. That is, if Ni ^{2 +} is slightly oxidized to Ni ^{3 +} , the z value will exceed 0. If all Ni ^{2 +} is oxidized to Ni ^{3 +} , the z value will have a value of 1. Therefore, the range of the z value is 0 < z < 1. This is controlled according to the amount of the oxidizing agent added in the step S200.

The preferred formulation of the LNMCO precursor powder according to one embodiment of the present invention is Ni _0.8 Co _0.1 Mn _0.1 (OH) _2.153 .

The valence state of nickel contained in the LNMCO precursor powder is a mixed state of Ni ^{2 +} and Ni ^{3 +} . This indicates that the pre-oxidation due to the addition of potassium permanganate (KMnO ₄ ) oxidizing agent has the effect of trivalent oxidation of the valence of nickel atoms.

After the step of filtering the LNMCO precursor powder is performed, the step of mixing the LNMCO precursor powder with a lithium (Li) source is performed (S400).

The Ni-rich LNMCO cathode material is prepared by mixing the LNMCO precursor powder with a source of lithium (Li), and the cathode material of the NCA series can also be prepared through the precursor powder containing aluminum as described above. According to one preferred embodiment of the present invention, lithium hydroxide hydrate (LiOH.H2O) is used as the lithium (Li) source.

Hereinafter, preferred examples of the preparation are described for the purpose of facilitating understanding of the present invention. However, the following Production Examples are for the purpose of helping understanding of the present invention, and the present invention is not limited by the following Production Examples.

The preferred Ni-rich LNMCOs prepared in the preparation and comparative examples of the present invention were prepared via a hydroxide coprecipitation method, which is essential for achieving a uniform chemical composition at the atomic level. In addition, by uniformly adjusting the particle size and shape, it is possible to achieve a high volumetric energy density.

&Lt; Comparative Example 1: LNMCO precursor powder not treated with an oxidizing agent (expressed by pristine precursor) >

(1) The stoichiometric amount corresponding to the molar ratio NiSO ₄ .6H ₂ O: CoSO ₄ .7H ₂ O: MnSO ₄ .6H ₂ O = 0.8: 0.1: 0.1 is dissolved together with deionized water to form a transparent mixed solution &Lt; / RTI &gt;

(2) The mixed solution was pumped into a continuously stirred tank reactor under N ₂ atmosphere. At the same time, an aqueous solution of NaOH and NH ₄ OH was added as a pH adjusting agent and a chelating agent, respectively.

(3) A coprecipitated spherical LNMCO precursor powder in the pumped mixed solution was filtered, washed several times with deionized water, and dried at 110 캜 for 24 hours to obtain an LNMCO precursor A pristine precursor was prepared.

&Lt; Comparative Example 2: Ni-rich LNMCO cathode material prepared by calcination in air atmosphere (expressed by Air-LNMCO) >

(1) The LNMCO precursor powder prepared in Comparative Example 1, which had not been treated with the oxidizing agent, was mixed with LiOH.H ₂ O (Li source).

② LNMCO pristine precursor mixed with LiOH · H ₂ O was preheated at 480 ° C. for 5 hours and then heated at 800 ° C. for 16 hours in air to prepare Air-LNMCO.

&Lt; Comparative Example 3: Ni-rich LNMCO cathode material prepared by calcination under a pure oxygen atmosphere (represented by Oxy-LNMCO) >

(1) The LNMCO precursor powder prepared in Comparative Example 1, which had not been treated with the oxidizing agent, was mixed with LiOH.H ₂ O (Li source).

② LNMCO pristine precursor mixed with LiOH · H ₂ O was preheated at 480 ° C. for 5 hours and then heated at 800 ° C. for 16 hours under pure oxygen atmosphere to prepare Oxy-LNMCO.

PREPARATION EXAMPLE 1: LNMCO precursor powder (designated as KMnO ₄ -treated precursor) prepared with the pre-oxidation process according to the present invention>

(1) The stoichiometric amount corresponding to the molar ratio NiSO ₄ .6H ₂ O: CoSO ₄ .7H ₂ O: MnSO ₄ .6H ₂ O = 0.8: 0.1: 0.1 is dissolved together with deionized water to form a transparent mixed solution &Lt; / RTI &gt;

(2) To the mixed solution, 0.2 mol% of KMnO ₄ (relative to the sum of the total molar amount of aqueous nickel solution, aqueous cobalt solution and aqueous manganese solution) was added.

(3) The mixed solution containing KMnO ₄ was pumped into a tank reactor which was continuously stirred under a N ₂ atmosphere. At the same time, an aqueous solution of NaOH and NH ₄ OH was added as a pH adjusting agent and a chelating agent, respectively.

(4) A coprecipitated spherical LNMCO precursor powder in the pumped mixed solution was filtered, washed several times with deionized water, and dried at 110 ° C for 24 hours to obtain KMnO ₄ LNMCO precursor powder (KMnO ₄ -treated precursor) pre-oxidized with an oxidizing agent was prepared.

PREPARATION EXAMPLE 2 Ni-rich LNMCO cathode material prepared with the preferred pre-oxidation process according to the present invention (denoted as KMnO ₄ -LNMCO)

(1) KMnO ₄ prepared in Preparation Example 1 LNMCO precursor powder (KMnO ₄ -treated precursor) pre-oxidized with an oxidizing agent was mixed with LiOH.H ₂ O (Li source).

(2) The LNMCO precursor powder (KMnO ₄ -treated precursor) mixed with LiOH.H ₂ O was preheated at 480 ° C. for 5 hours and then heated at 800 ° C. for 16 hours in an air atmosphere to prepare KMnO ₄ -LNMCO.

2 is an SEM image of the LNMCO precursor powder prepared in Comparative Example 1 of the present invention and Production Example 1 of the present invention.

More specifically, the SEM image of the LNMCO pristine precursor particles prepared in Comparative Example 1 and the SEM image further enlarged to observe the surface of the pristine precursor particles are shown in FIGS. 2 (a) and 2 (b) and an SEM image of the LNMCO treated precursor particles prepared in Preparation Example 1 and a SEM image further enlarged to observe the surface of the particles of the treated precursor are shown in FIG. 2 (c) ) And (d).

Referring to FIG. 2, it can be seen that both precursors are composed of a large number of nano-sheets and have a spherical structure. Secondary spherical particles of the two precursors are uniformly distributed, and it can be confirmed that the average particle diameter is 10 탆.

3 is an XPS spectrum of the LNMCO precursor powder prepared in Comparative Example 1 of the present invention and Production Example 1 of the present invention.

More specifically, X-ray photoelectron spectroscopy (XPS) measurements were performed using an AXIS Ultra DLD spectrometer with Al K? (Excitation, 1486.6 eV) radiation, The oxidation state of nickel, cobalt and manganese on the surface of the prepared LNMCO precursor was measured and shown in Figs. 3 (a), 3 (b) and 3 (c) respectively.

Referring to FIG. 3, Ni 2p, Mn 2p and Co 2p spectra of a non-oxidized precursor and an oxidized precursor (KMnO ₄ -treated precursor) can be confirmed.

When Fig. 3 (b) and FIG. 3 (c), in both precursor Mn 2p _3/2 peak was observed in 642.13eV and 654.08eV, Co 2p _3/2 peak was observed at 781.38eV and 797.13eV. This peak corresponds to the XPS results for the Mn ^{4 +} and Co ³⁺ previously reported. Therefore, it can be seen that the valence states of Mn and Co of the un-oxidized precursor and the oxidized precursor (KMnO ₄ -treated precursor) are similar.

On the other hand, it can be confirmed that the pristine precursor and the oxidized precursor (KMnO ₄ -treated precursor), which are not oxidized, have different valence states of nickel.

Referring to FIG. 3 (a), it can be seen that a peak of 856.08 eV is observed in both precursors. This peak corresponds to the XPS results for the Ni ^{2 +} previously reported. Further, it can be confirmed that a peak of 857.98 eV is observed only in the oxidized precursor (KMnO ₄ -treated precursor). These peaks are consistent with the previously reported XPS results for Ni ³⁺ .

That is, the valence state of nickel near the surface of the LNMCO precursor (KMnO ₄ -treated precursor) oxidized with KMnO ₄ is a mixed state of Ni ^{2 +} and Ni ^{3 +} . This result shows that KMnO ₄ can oxidize Ni ^{2 +} to Ni ^{3 +} according to the following formula (1).

[Chemical Formula 1]

Mn ⁷⁺ + 3Ni ²⁺ ? Mn ⁴⁺ + 3Ni ³⁺

The Ni ^{2 +} and Ni ^{3 +} fractions of the total Ni contents were calculated from the quantitative XPS results (area of the deconvoluted peak). As a result, it was found that the non-oxidized precursor and the oxidized precursor (KMnO ₄ -treated precursor) The Ni ^{3 +} / Ni ²⁺ ratios were 0 and 0.237, respectively.

These results suggest that KMnO ₄ Pre-oxidation through an oxidant can actually prove effective in the oxidation of nickel (Ni) in the LNMCO precursor, and the amount of oxidant added can be controlled to control the ratio of nickel atomic states near the LNMCO precursor powder surface And a desired oxidation state can be obtained.

4 is an FTIR graph of the LNMCO precursor powder prepared in Comparative Example 1 of the present invention and Production Example 1 of the present invention.

More specifically, the interactions of functional groups and functional groups of the LNMCO precursor prepared in Comparative Example 1 and Production Example 1 were measured through a Fourier transform infrared (FTIR) spectrometer (Excalibur series FTS 3000 Bio-Rad spectrometer).

Referring to Fig. 4, the sharp peak observed at 3500-3626 cm ^{& lt} ; -1 &gt; is the peak indicating the hydroxyl group. Peaks for anions other than hydroxyl groups were not found in the spectrum, indicating that the precursor Ni _{0 . 8} Co _{0 . 1} Mn _{0 .1} (OH) _{2 + z} .

The value of z may be determined by the valence state of each transition metal ion (Ni, Co and Mn) in the precursor and will increase in proportion to the fraction of Ni ^{3 +} to meet the neutral condition. Based on the XPS results, the z values of the un-oxidized precursor and the oxidized precursor (KMnO ₄ -treated precursor) were calculated to be 0 and 0.153, respectively. Therefore, it can be seen that 0 < z < 1 according to the fraction of Ni ^{3 +} of the LNMCO precursor as described above.

5 is a SEM image of Ni-rich LNMCO prepared in Comparative Example 2, Comparative Example 3 and Preparation Example 2 of the present invention.

More specifically, an SEM image of the air-LNMCO particles prepared in Comparative Example 2 and a SEM image further enlarged to observe the surface of the air-LNMCO particles are shown in FIGS. 5 (a) and 5 (b) SEM images of the Oxy-LNMCO particles prepared in Comparative Example 3 and SEM images further enlarged to observe the surface of the Oxy-LNMCO particles are shown in Figs. 5 (c) and 5 (d) the KMnO ₄ shows an SEM image and a further enlarged SEM image for observing the surface of the particles of the KMnO ₄ -LNMCO -LNMCO particles to 5 (e) and (f) respectively.

Referring to FIG. 5, it can be seen that the particle size of the LNMCO anode material in all samples (Air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO) has an average particle diameter of 10 μm, which is equal to the particle size of the LNMCO precursor .

However, it can be seen that the nano-sheet structure observed in the LNMCO precursor is melted in the heat treatment process and changed into a particle structure of 100 to 300 nm in size, thereby covering the surface of the LNMCO cathode material.

6 is an XRD graph of Ni-rich LNMCO prepared in Comparative Example 2, Comparative Example 3 and Production Example 2 of the present invention.

More specifically, Comparative Example 2 (Air-LNMCO) was performed by performing X-ray diffraction (XRD) measurement at 10 ° to 80 ° at a refresh rate of 4 ° × min ¹ using Rigaku D Max / 2000 PC with CuKα radiation. , The crystal structure of Ni-rich LNMCO prepared in Example 3 (Oxy-LNMCO) and Production Example 2 (KMnO ₄ -LNMCO) was measured.

6, the XRD patterns of all the samples (Air-LNMCO, Oxy-LNMCO, and KMnO ₄ -LNMCO) have the same hexagonal α-NaFeO ₂ structure as the R3m space group And an extra diffraction peak was not observed, so that it was confirmed that there was no impurity phase in the prepared sample.

In addition, Applicants measured unit cell parameters of all samples (Air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO) and summarized the results in Table 1 below.

Sample a c c / a Rw Air-LNMCO 2.8748 14.211 4.9432 1.3891 Oxy-LNMCO 2.8750 14.222 4.9458 1.6835 KMnO ₄ -LNMCO 2.8756 14.226 4.9470 1.4799

Referring to Table 1, the lattice constants of the c-axis slightly increase in the order of Air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO, but the lattice constants of the a-axis are almost the same. C / a value of KMnO ₄ -LNMCO is higher than the c / a value of the other sample, which indicates that the KMnO ₄ -LNMCO the Li ⁺ insertion / de-insertion (intercalation / de-intercalation) to the more favorable structure, such a construction is discharged This has a positive effect on the rate capabilities.

The integral intensity ratio Rw is greater than 1.2. This means that all samples (Air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO) indicates that the cation has a lower failure (low degree of cation disorder) between Li ⁺ and Ni ^{+ 2,} has a good hexagonal arrangement. Here, the integral intensity ratio Rw is the width of the (003) peak / (104) peak in FIG. 6 (Rw = (I003) / (I104)

These XRD results demonstrate that the LNMCO precursor treatment with oxidants plays a role in helping to have a well-ordered layered structure.

7 is an XPS spectrum of Ni-rich LNMCO prepared in Comparative Example 2, Comparative Example 3 and Production Example 2 of the present invention.

More specifically, X-ray photoelectron spectroscopy (XPS) measurements were performed using an AXIS Ultra DLD spectrometer with Al K? (Excitation, 1486.6 eV) radiation, And the oxidation state of nickel, cobalt and manganese on the surface of Ni-rich LNMCO prepared in Production Example 2 were measured and shown in Figs. 7 (a), 7 (b) and 7 (c), respectively.

Referring to FIG. 7, Ni 2p, Mn 2p and Co 2p spectra of Air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO can be confirmed.

Main peaks of Figure 7 (b) and Mn 2p _3/2 in Fig. 7 (c) Referring to, all of the samples (Air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO) was observed at 642.2eV, Co2p _{3 /} The main peak of ₂ was observed at around 780.01 eV. This peak corresponds to the XPS results for the Mn ^{4 +} and Co ^{3 +} previously reported. Therefore, it can be seen that the valence states of Mn and Co of all the samples (Air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO) are similar.

Referring to Figure 7 (a), the main peak of the Ni 2p _3/2 in the KMnO ₄ was observed in -LNMCO 855.85eV, which is very close to the main peak (856.35eV) of the Ni 2p _3/2 in the Oxy-LNMCO. This proves that the valence state of Ni in both samples (KMnO ₄ -LNMCO and Oxy-LNMCO) is a mixture of 2+ and 3+, and that Ni ³⁺ / Ni ² in air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO ^{+ Is} measured as 1.22, 1.56 and 1.96, respectively. These results show that the Ni-rich LNMCO precursor Ni _{1 -xy} Co _x Mn _y (OH) _{2 + z} (0 <x? 0.4, 0 <y? 0.4, 0 <x + y? 0.5, The adjustment of the ratio of nickel atomic states (adjusting the z value) through the addition of an oxidizing agent during manufacture means that the ratio of nickel atomic states near the surface of the Ni-rich LNMCO cathode material made of the Ni-rich LNMCO precursor is controlled.

As described in FIG. 3, the valence state of nickel near the surface of the LNMCO precursor treated with KMnO ₄ is a mixed state of Ni ²⁺ and Ni ^{3 +} . This apparently seems to increase the fraction of Ni ^{3 +} in LNMCO. As the valence state of the nickel ion increases from 2 to 3, the mixing between the Li ⁺ and Ni ^{2 +} cations will decrease and the lower cation mixing will show better electrochemical performance. In addition, Li ⁺ and Ni ^{2 +} low cation disorder (low degree of cation disorder) between the means that can generate a more stable floor structure.

A coin-type cell was fabricated using the Ni-rich LNMCO prepared in Comparative Example 2, Comparative Example 3 and Preparation Example 2 according to the present invention, and the electrochemical characteristics of the Ni-rich LNMCO cathode material . It should be understood, however, that the following examples are intended to aid in the understanding of the present invention and are not intended to limit the scope of the present invention.

Experimental Example

The positive electrode active material of 80% by weight on an aluminum foil (Air-LNMCO, Oxy-LNMCO and KMnO ₄ -LNMCO), 10% by weight of carbon black (Super P), and 10% by weight of polyvinylidene fluoride (of poly- vinylidene fluoride) binder. Further, lithium metal was used as a counter electrode, and a microporous polyethylene separator was inserted between the positive electrode and the counter electrode. As the electrolyte, LiPF ₆ was dissolved in ethylene carbonate / dimethyl carbonate (1: 1, v / v).

FIG. 8 is a graph showing charge / discharge characteristics of coin-type cells manufactured using the Ni-rich LNMCO anode materials prepared in Comparative Examples 2, 3, and 2 of the present invention.

More specifically, the initial charge / discharge curves of the coin-type cells are shown in FIG. 8 (a) at a voltage between 3.0 and 4.3 V at 25 ° C. and a constant current density of 18.5 mAg ^-1 , 8 (b) shows the result of evaluating the cycle stability of the coin-type cells under a constant current density condition of a voltage of 4.3 V and a current density of 185.0 mAg- ¹ (1C rate).

8A, the initial charge / discharge capacities of the Air-LNMCO coin-type cell, the Oxy-LNMCO coin-type cell and the KMnO ₄ -LNMCO coin-type cell are 239/191, 241/193 and 228/190 mAh x g ¹ . These data are described in more detail in Table 2 below.

Sample Charge capacity
(mAh x g ^-1 ) Discharge capacity
(mAh x g ^-1 ) Coulomb efficiency
(Coulombic efficiency)
(%) Air-LNMCO 239.561 191.481 79.92 Oxy-LNMCO 241.438 193.731 80.24 KMnO ₄ -LNMCO 228.131 190.601 83.54

The results shown in Table 2 can be explained by the fact that the Oxy-LNMCO cathode material and the KMnO ₄ -LNMCO cathode material generate a better layered structure.

As shown in FIG. 8 (a), the charge plateau of the Air-LNMCO coin-type cell is the charge plateau of the Oxy-LNMCO coin-type cell and the KMnO ₄ -LNMCO coin- plateau, indicating that higher activation energy is needed in the delithiation process of the Air-LNMCO coin-type cell.

Referring to FIG. 8 (b), after 100 cycles, the Air-LNMCO coin-type cell and the Oxy-LNMCO coin-type cell exhibit a discharge capacity of 154 and 161 mAh x g ¹ , respectively, And a capacity retention rate of 93%. In addition, after 100 cycles, the KMnO ₄ -LNMCO coin-type cell can provide a discharge capacity of 163 mAh x g ¹ , which means that it exhibits a high capacity retention rate of 95%.

That is, the more stable structure of the KMnO ₄ -LNMCO cathode material stabilizes the lithiation of the battery cell, thereby making it possible to manufacture a cell having a higher capacity retention rate.

FIG. 9 is a graph showing charge / discharge characteristics of coin-type cells manufactured using the Ni-rich LNMCO anode materials prepared in Comparative Examples 2, 3, and 2 of the present invention at higher voltages.

More specifically, to further investigate the electrochemical performance of coin-type cells at higher voltages, the upper cut-off voltage was raised from 4.3V to 4.5V. The initial charge / discharge curves of the coin-type cells are shown in Figure 9 (a) at a voltage between 3.0 and 4.5 V at 25 ° C and a constant current density of 18.5 mAg ^-1 , and between 3.0 and 4.5 V at 25 ° C And the cycle stability of the coin-type cells was evaluated under a constant current density condition of 185.0 mAg- ¹ (1C rate), as shown in FIG. 9 (b).

9A, the initial charge / discharge capacities of the Air-LNMCO coin-type cell, the Oxy-LNMCO coin-type cell and the KMnO ₄ -LNMCO coin-type cell are 233/208, 238/210 and 233/209 mAh x g ¹ .

9 (b), after 100 cycles, Oxy-LNMCO coin-type cells and KMnO ₄ -LNMCO coin-type cells exhibited capacity retention ratios of 82% and 72%, respectively, And a low capacity maintenance rate of 52%.

In general, irreversible structural changes easily occur at the cathode (anode) electrode because high upper cut-off voltage extracts more Li ⁺ ions from the cell's lattice. This leads to a reduction in cell capacity.

In addition, cationic mixing induced by ion transfer dramatically increases the kinetic barrier to reversible de / intercalation of Li ⁺ ions during the cycle, greatly increasing the electrode interface resistance, .

7, the KMnO ₄ -LNMCO cathode material has a low Ni ^{2 +} content and a high Ni ^{3 +} content, which stabilizes the structure of the cell during high voltage cycling and leads to better electrochemical properties .

FIG. 10 is a graph showing the discharge capacity ratio (rate capability) according to the charge / discharge rate (C rate) of coin-type cells manufactured using the Ni-rich LNMCO anode materials prepared in Comparative Examples 2, 3, .

More specifically, the discharge capability ratio of Air-LNMCO coin-type cell, Oxy-LNMCO coin-type cell and KMnO ₄ -LNMCO coin-type cell was measured at various current density conditions of 0.1C to 7C, and 3.0 Capacitance recovery when returning to 0.1 C in the voltage range of ~ 4.3 V (vs. Li + / Li) was measured.

Referring to Figure 10, Oxy-LNMCO coin-type cell and KMnO ₄ -LNMCO coin-type cell Air-LNMCO coin-type exhibits a high discharge capacity than the cells. Particularly, the discharge capacity of coin-type cells of Air-LNMCO greatly decreases at high charge / discharge rates (from 3C to 7C).

All the samples recovered their original discharge capacity when the current density returned to 0.1 C, which implies that the decrease in capacity at high current density is a decrease in capacity due to cation migration induced by ion transport rather than irreversible structural change .

That is, a cell made with a KMnO ₄ -LNMCO cathode material with a low cationic mix can exhibit better properties at higher current densities. In fact, the KMnO ₄ -LNMCO coin-type cell has the highest Discharge capacity ratio (rate capability).

KMnO ₄ -LNMCO and KMnO ₄ -LNMCO coin-type cells were prepared using pre-oxidized LNMCO precursors via an oxidant as described above, and their physical and chemical properties were measured.

Physical properties measurements have shown that pre-oxidation (KMnO ₄ treatment) oxidizes Ni ^{2 +} to Ni ^{3 +} in the LNMCO precursor through XPS analysis. The ratio of Ni ^{3 +} in KMnO ₄ -LNMCO was higher than that of Air-LNMCO and almost identical to that of Oxy-LNMCO. In addition, XRD analysis showed that KMnO ₄ treatment had little effect on the crystal structure of LNMCO and lowered the cation disorder.

As a result of the chemical property measurement, it was confirmed that the KMnO ₄ -LNMCO coin-type cell showed equivalent or better discharge capability and cycling stability as compared with the Oxy-LNMCO coin-type cell.

In addition, pre-oxidation of the precursor of the Ni-rich cathode material is an efficient and simple process from a cost point of view and proved that excellent Ni-rich cathode material can be provided without the calcination process in the pure oxygen atmosphere.

Claims (9)

A method for producing a nickel-based cathode material,
Preparing a mixed solution having a nickel aqueous solution, a cobalt aqueous solution and a manganese aqueous solution;
Adding an oxidizing agent to the mixed solution;
Filtering the LNMCO precursor powder in the mixed solution to which the oxidizing agent is added; And
And mixing the LNMCO precursor powder with a lithium source. &Lt; RTI ID = 0.0 &gt; 18. &lt; / RTI &gt; The method according to claim 1, wherein the molar ratio of the nickel aqueous solution, the aqueous solution of cobalt and the aqueous solution of manganese is 1-xy: x: y (0 <x? 0.4, 0 <y? 0.4, 0 <x + y? 0.5) Gt; Ni-rich &lt; / RTI &gt; LNMCO cathode material. The method according to claim 1,
The nickel aqueous solution, the cobalt aqueous solution and the manganese aqueous solution are each an aqueous solution of nickel sulfate (NiSO ₄ .6H ₂ O), an aqueous solution of cobalt sulfate (CoSO ₄ .7H ₂ O) and a solution of manganese sulfate (MnSO ₄ .6H ₂ O) Gt; Ni-rich &lt; / RTI &gt; LNMCO cathode material. The method according to claim 1,
Wherein the oxidizing agent is potassium permanganate (KMnO ₄ ). The method according to claim 1,
Wherein the amount of the oxidizing agent in the step of adding the oxidizing agent to the mixed solution is not more than 10 mol% with respect to the sum of the total moles of the aqueous nickel solution, aqueous solution of cobalt and aqueous solution of manganese. The method according to claim 1,
The formula of the LNMCO precursor powder is Ni _{1 -x- y} Co _x Mn _y (OH) _{2 + z} (0 <x? 0.4, 0 <y? 0.4, 0 <x + y? 0.5, 0 <z < Wherein the Ni-rich LNMCO anode material is a Ni-rich LNMCO cathode material. The method according to claim 1,
Wherein the valence state of the nickel contained in the LNMCO precursor powder is a mixed state of Ni ^{2 +} and Ni ^{3 +} . The method according to claim 1,
Wherein the lithium source is lithium hydroxide. &Lt; RTI ID = 0.0 &gt; 15. &lt; / RTI &gt; The Ni-rich LNMCO cathode material according to any one of claims 1 to 8, wherein the Ni-rich LNMCO cathode material has a layered structure.

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