KR20200047960A - Cathode active material with coating layer formed and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a positive electrode active material with a coating layer formed on a surface and inside, wherein the coating layer includes lithium (Li) ion conductive oxide and amorphous carbon (C), and the lithium ion conductive oxide contains carbonate (CO_3^-).

Description

Cathode active material with coating layer formed and manufacturing method thereof

The present invention relates to a positive electrode active material having a coating layer and a method for manufacturing the same, and more particularly, to a positive electrode active material including a non-transition metal-based lithium precursor derivative and a method for manufacturing the same.

Today, secondary batteries are widely used as high-performance energy sources with high energy densities from large-capacity power storage batteries such as automobiles and power storage systems to small portable electronic devices such as mobile phones, camcorders, and laptops, and as the field of application of secondary batteries expands, From small products such as mobile phones and laptops, demand is gradually increasing in various fields, from medium to large electric vehicles and energy storage systems.

In particular, a lithium secondary battery, which is one of secondary batteries, has advantages of higher energy density, higher capacity per unit area, lower self-discharge rate, and longer service life than nickel-manganese batteries or nickel-cadmium batteries. In addition, it has no memory effect, so it has the characteristics of convenience and long life. However, as a battery for a next-generation electric vehicle, a lithium ion battery has problems such as stability problems due to overheating, low energy density, and low power. Particularly, since lithium secondary batteries use flammable organic solvents as electrolyte solvents, there is a high probability of fire and explosion when a short circuit occurs due to physical damage, and a number of accidents actually occur. Accordingly, in recent years, in order to increase safety, interest in an all-solid-state battery using a solid electrolyte rather than a liquid electrolyte as an electrolyte has increased.

In addition to the development of a solid electrolyte having excellent ion conductivity in the field of the entire solid battery, an improvement in performance of the entire solid battery has been attempted by paying attention to the interfacial reaction between the solid electrolyte and the positive electrode active material. From the viewpoint of improving battery performance, there is a need to improve battery performance by reducing resistance between a positive electrode active material and a solid electrolyte and increasing conductivity.

Recently, a method of using a composite form of a transition metal oxide-based nanoparticle coating such as a Nb material positive electrode active material (for example, a positive electrode active material coated with LiNbO ₃ ) has been attempted, but the surface modification effect is insufficient and the Nb material and spray coating process are used. Due to this, the problem of high cost of the process has emerged.

International Publication Patent No. 2007-004590 Japanese Patent Publication No. 2011-090877

The problem to be solved by the present invention is to provide a positive electrode active material formed with a coating layer comprising an amorphous carbon and a lithium ion conductive material.

In addition, an object of the present invention is to provide a positive electrode active material capable of improving battery performance such as battery conductivity without causing an increase in battery resistance compared to the prior art.

In addition, it is an object of the present invention to provide a method of manufacturing a positive electrode active material including a coating layer having a uniform distribution, in which a derivative is formed from a lithium-containing precursor by a sol-gel method, unlike the conventional Nb material positive electrode active material production.

The object of the present invention is not limited to the object mentioned above. Other specific matters of the present invention are included in the detailed description and drawings.

The positive electrode active material according to the present invention for achieving the above object is a positive electrode active material with a coating layer formed on the surface and inside, the coating layer comprising lithium (Li) ion conductive oxide and amorphous carbon (C), the lithium ion conductive oxide Silver carbonate (CO ₃ ⁻ ).

The concentration of the carbonate may be 5000 ppm to 16000 ppm.

The concentration of the carbonate may be 10000 ppm to 16000 ppm.

The amorphous carbon may include 0.2 w% to 1.0 w%.

The lithium ion conductive oxide may be selected from the group consisting of lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium peroxide (Li ₂ O ₂ ), and combinations thereof.

In addition, a method of manufacturing a positive electrode active material having a coating layer according to the present invention includes preparing a positive electrode active material; Forming a mixture by adding a lithium (Li) -containing precursor to the positive electrode active material; And calcining the mixture, and calcining the mixture may include forming a coating layer containing a lithium ion conductive oxide derived from the lithium-containing precursor.

In the step of forming the mixture, with respect to 100 parts by weight of the positive electrode active material, the lithium-containing precursor may be added in an amount of 0.1 to 5 parts by weight.

In the step of forming the mixture, the lithium-containing precursor may include lithium ethoxide (CH ₃ CH ₂ OLi).

The step of firing the mixture is carried out under a gas atmosphere selected from the group consisting of nitrogen (N ₂ ), oxygen (O ₂ ), argon (Ar), air (Air), and combinations thereof, a coating layer may be formed. have.

The step of firing the mixture may be performed at a temperature of 300 ° C to 500 ° C.

The step of calcining the mixture may be performed for 1 hour to 4 hours.

The lithium-ion conductive oxide, carbonate (CO ₃ ^-) may include.

The carbonate may be included in a concentration of 5000 ppm to 16000 ppm.

The carbonate may be contained in a concentration of 10000 ppm to 16000 ppm.

The coating layer may further include amorphous carbon (C), and may include the amorphous carbon at 0.2 w% to 1.0 w%.

The lithium ion conductive oxide may be selected from the group consisting of lithium tansium (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium peroxide (Li ₂ O ₂ ), and combinations thereof.

In addition, the positive electrode active material on which the coating layer according to the present invention is formed may be manufactured by the above-described manufacturing method.

Details of other embodiments are included in the detailed description and drawings.

A battery using a positive electrode active material with a coating layer formed in accordance with some embodiments of the present invention, despite a high concentration of carbonate, does not cause an increase in resistance and battery conductivity may be improved.

In addition, since the present invention uses a positive electrode active material coated with a derivative of a lithium-containing precursor, the coating uniformity can be improved more than the conventional positive electrode active material.

In addition, since the non-transition metal-based lithium precursor derivative forms a uniform coating layer by a sol-gel method, compared to the spray coating process used to manufacture the cathode active material for Nb materials, it not only reduces process cost but also improves cell performance when applied to batteries. Can be.

The effects of the present invention are not limited to the effects mentioned above. It should be understood that the effects of the present invention include all effects that can be deduced from the following description.

1 is a view schematically showing a positive electrode active material according to an embodiment of the present invention.
2 is a conceptual diagram illustrating a method of manufacturing a positive electrode active material according to an embodiment of the present invention.
3 is a flowchart schematically showing a method of manufacturing a positive electrode active material according to an embodiment of the present invention.
4 is a result of measuring the particle size of Example 1 and Comparative Example 1 of the present invention.
5 (a) and 5 (b) are X-ray diffraction spectoscopy (XRD) result images showing the grain crystal structures of Example 1 and Comparative Example 1 of the present invention, respectively.
6 is an FT-IR analysis result image of Comparative Example 1 of the present invention.
7 is a scanning electron microscopy (SEM) image of Comparative Example 1 of the present invention.
8 is an SEM image of Example 1 of the present invention.
9 is a transmission electron microscopy (TEM) image of Comparative Example 1 of the present invention and an energy-dispersive X-ray spectroscopy (EDS) result image.
10 and 11 are TEM image and EDS result image of Example 1 of the present invention.
12 (a) to 12 (c) are X-ray photoelectron spectroscopy (XPS) analysis images comparing carbon (C), lithium (Li), and oxygen (O) atomic ratios of Example 1 of the present invention, respectively.
13 is an X-ray diffraction analysis (X-ray Photoelectron Spectroscopy, XRD) result image of Example 1 of the present invention and LiCO ₃ included therein.
14A and 14B are evaluation images showing initial charge / discharge characteristics and charge / discharge cycle characteristics for a half cell including Example 1 and Comparative Example 1 of the present invention, respectively.
15 is an evaluation image showing initial charge / discharge characteristics for a full cell including Example 1 and Comparative Example 1 of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to completely inform the person having the scope of the invention, and the present invention is only defined by the scope of the claims. The same reference numerals refer to the same components throughout the specification.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings commonly understood by those skilled in the art to which the present invention pertains. In addition, terms defined in the commonly used dictionary are not ideally or excessively interpreted unless explicitly defined.

In addition, the terminology used herein is for describing the embodiments and is not intended to limit the present invention. In the present specification, the singular form also includes the plural form unless otherwise specified in the phrase. As used herein, “comprises” and / or “includes” one or more other components, features, numbers, steps and / or actions other than the components, features, numbers, steps and / or actions mentioned It is used in a sense that does not exclude the presence or addition of an action. And, “and / or” includes each and every combination of one or more of the mentioned items.

In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case of being "directly above" the other part but also another part in the middle. Conversely, when a portion of a layer, film, region, plate, or the like is said to be “under” another portion, this includes not only the case “underneath” another portion, but also another portion in the middle.

Unless otherwise specified, all numbers, values, and / or expressions expressing the amounts of ingredients, reaction conditions, polymer compositions, and blends used herein are those numbers that occur in obtaining these values, among others. As these are approximations that reflect the various uncertainties of the measurement, it should be understood that in all cases they are modified by the term "about". In addition, when numerical ranges are disclosed in this description, these ranges are continuous, and include all values from the minimum value in this range to the maximum value including the maximum value, unless otherwise indicated. Further, when such a range refers to an integer, all integers including the minimum value to the maximum value including the maximum value are included unless otherwise indicated.

In the present specification, when a range is described for a variable, it will be understood that the variable includes all values within the described range including the described endpoints of the range. For example, a range of “5 to 10” includes values of 5, 6, 7, 8, 9, and 10, as well as any subrange of 6 to 10, 7 to 10, 6 to 9, 7 to 9, and the like. It will be understood to include, and include any value between integers pertinent to the stated range of ranges such as 5.5, 6.5, 7.5, 5.5 to 8.5 and 6.5 to 9, and the like. Also, for example, the range of “10% to 30%” is 10% to 15%, 12% to 10%, 11%, 12%, 13%, etc., and all integers including up to 30%. It will be understood that it includes any subranges such as 18%, 20% to 30%, etc., and also includes any value between valid integers within the scope of the stated range, such as 10.5%, 15.5%, 25.5%, and the like.

Hereinafter, the present invention will be described in more detail according to the accompanying drawings.

1 is a view schematically showing a positive electrode active material according to an embodiment of the present invention. Referring to Figure 1, the positive electrode active material 10 according to the present invention may include a coating layer 30 on the surface and the inside. Meanwhile, FIG. 1 shows only the coating layer 30 formed on the surface of the positive electrode active material 10, but is not limited thereto.

In addition, the coating layer 30 formed on the positive electrode active material 10 according to the present invention may include lithium (Li) ion conductive oxide and amorphous carbon (C).

Meanwhile, in the present invention, the lithium ion conductive oxide may be selected from the group consisting of lithium tansium (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium peroxide (Li ₂ O ₂ ), and combinations thereof. In particular, the lithium ion conductive oxide in the coating layer 30 according to the present invention may preferably include carbonate (CO ₃ ⁻ ).

Meanwhile, the amorphous carbon in the present invention may be preferably included in 0.2 w% to 1.0 w%.

What distinguishes the positive electrode active material 10 of the present invention from the conventional positive electrode active material is that the coating layer 30 including amorphous carbon and lithium ion conductive oxide (for example, lithium carbonate (Li ₂ CO ₃ )) is a positive electrode active material. (10) As it is coated uniformly (homogeneous) not only inside, but also outside, it does not cause an increase in resistance (for example, an entire solid cell) containing the battery and the battery conductivity may increase. .

On the other hand, the carbonate (CO ₃ ^-) when the positive electrode active material if it is included is, increasing the content of the carbonate is a study that the conductivity cell deterioration. Accordingly, the appropriate carbonate concentration of the conventionally known positive electrode active material is approximately 2000 ppm to 3000 ppm.

However, in the positive electrode active material 10 of the present invention, the carbonate (CO ₃ ^-) despite the increase in the content of, and rather may be cell conductivity is improved and enhanced. More specifically, the carbonate may be included in the positive electrode active material 10 according to the present invention at a concentration of 5000 ppm to 16000 ppm. Preferably, the concentration of carbonate may be 10000 ppm to 16000 ppm. Although the positive electrode active material 10 of the present invention contains carbonate at a value significantly higher than a suitable concentration of a known carbonate, the coating layer 30 containing carbonate does not aggregate inside and outside the positive electrode active material 10 As it is uniformly coated, conductivity may be increased without causing an increase in battery resistance.

In addition, the coating layer 30 may further include amorphous carbon, and when the concentration of amorphous carbon is included in 0.2 w% to 1.0 w%, the effect of improving the conductivity of the present invention may be maximized.

Meanwhile, the coating layer 30 may be continuously coated along the surface or the inner surface of the positive electrode active material 10, or a plurality of layers may be dispersed and uniformly distributed on the positive electrode active material 10. That is, the coating layer 30 is not limited to the form shown in FIG. 1 and may be formed on the positive electrode active material in various forms. For example, the coating layer 30 may be formed in contact with the outside and inside of the positive electrode active material 10 in the form of a plurality of particles.

In addition, at least one of the plurality of particles may include lithium ion conductive oxide, or may be formed by being uniformly dispersed outside and inside the positive electrode active material 10 including amorphous carbon. Preferably, the particles of the plurality of coating layers 30 may include both lithium ion conductive oxide and amorphous carbon.

2 and 3 are each a schematic view and a flow chart schematically showing a method of manufacturing a positive electrode active material according to an embodiment of the present invention. For convenience of explanation, differences from those described with reference to FIG. 1 will be mainly described.

First, referring to Figure 2, the method of manufacturing a positive electrode active material according to the present invention, a non-transition metal-based lithium precursor through a calcination (calcination) lithium-containing derivative is uniformly formed to produce a coating layer on the positive electrode active material, sol gel ( The sol-gel) method is shown.

Subsequently, with reference to FIG. 3, a method of manufacturing the positive electrode active material (see FIG. 1) according to the present invention includes preparing a positive electrode active material (S100) and the lithium (Li) -containing precursor (precursor). It may include the step of forming a mixture by adding to the active material (S110) and firing the mixture (S120), and as a result, a positive electrode active material having a coating layer may be prepared (S130).

In the step of forming the mixture of the present invention (S110), with respect to 100 parts by weight of the positive electrode active material, the lithium-containing precursor may be added in 0.1 to 5 parts by weight. In particular, the lithium-containing precursor added to the mixture may include lithium ethoxide (CH ₃ CH ₂ OLi). For example, as the lithium-containing precursor of the present invention, preferably, lithium ethoxide may be added in 1 part by weight based on 100 parts by weight of the positive electrode active material.

More specifically, the step of forming the mixture (S110), for example, by adding a lithium-containing precursor in a solvent (for example, ethanol (Ethanol)) to dissolve, and then the positive electrode active material is introduced and dried while mixing . Thereafter, the firing step 120 may proceed.

On the other hand, in the step (S120) of sintering the mixture of the present invention, the lithium ion conductive oxide may be formed as a derivative from the lithium-containing precursor S110 previously added. Accordingly, a coating layer including a lithium ion conductive oxide (eg, lithium carbonate (Li ₂ CO ₃ )) may be formed (S130).

In addition, the step (S120) of calcining the mixture of the present invention is performed under a gas atmosphere selected from the group consisting of nitrogen (N ₂ ), oxygen (O ₂ ), argon (Ar), air (Air), and combinations thereof. Can be. Preferably, the firing step (S120) of the present invention may be performed under a nitrogen atmosphere.

In addition, the firing of the mixture in the present invention (S120), may be performed at a temperature of 300 ℃ to 500 ℃. In addition, calcination of the mixture (S120) may be performed for 1 hour to 4 hours. Preferably, the firing of the present invention can be carried out, for example, at a temperature of 370 ° C. for about 3 hours.

On the other hand, the positive electrode active material (see 10 in FIG. 1) produced by the manufacturing method (S100 to S130) of the present invention has a coating layer (see 30 in FIG. 1) comprising an ion conductive oxide and amorphous carbon (C) on the surface and inside. It can be formed homogeneously. Thus the anodic oxide coating layer is manufactured is preferably a carbonate (CO ₃ ^-) as a lithium-ion conductive oxide may include. In addition, such a lithium ion conductive oxide carbonate may be included at a concentration of 5000 ppm to 16000 ppm (for example, 12000 ppm).

Hereinafter, the present invention will be described in more detail through Examples and Comparative Examples. However, the following examples are for illustrative purposes only, and the scope of the present invention is not limited to these examples.

Example 1: Preparation of a positive electrode active material with a coating layer

Anode active material
[Parts by weight] Lithium ethoxide
(Lithum ethoxide, Sigma-Aldrich)
[Parts by weight] Example 1 100 One Comparative Example 1 100 -

As shown in Table 1, Example 1 is a positive electrode active material [NCM711 (Li (Ni _0.7 Co _0.15 Mn _0.15 ) O ₂ ) used] 100 w% of lithium ethoxide (Lithum ethoxide) 1 w% to ethanol was added Then mix to dissolve. Then, the positive electrode active material was added and dried while mixing at 60 ° C, followed by calcination at 370 ° C for 3 hours under a nitrogen atmosphere.

The components and concentrations of the positive electrode active material on which the coating layer prepared according to Example 1 was formed are shown in Table 2 below.

Comparative Example 1: Preparation of a conventional positive electrode active material

In the case of Comparative Example 1, only the positive electrode active material of the same kind and the same amount as in Example 1 was added without adding lithium ethoxide.

Thus, the components and concentrations of the positive electrode active material according to Comparative Example 1 are shown in Table 2 below.

Li ₂ CO ₃ [ppm] LiOH [ppm] Example 1 10000 ~ 16000 4000 Comparative Example 1 4000 4000

Referring to Table 2, while the concentrations of lithium hydroxide (LiOH) of Example 1 and Comparative Example 1 are the same, the concentrations of lithium carbonate (Li ₂ CO ₃ ) of Example 1 are significantly higher from 10000 to 16000 ppm. Was measured.

Evaluation Example 1: Size, shape and structure evaluation

4 is a result of measuring the particle size of Example 1 and Comparative Example 1 of the present invention. The particle size distribution was analyzed using (Cilas1090, Scinco).

4, the particle sizes of Example 1 and Comparative Example 1 can be compared, and are shown in Table 3 below.

Particle size D ₁₀ [mm] D ₅₀ [mm] D ₉₀ [mm] Example 1 4.04 7.27 12.15 Comparative Example 1 4.00 7.25 12.25

In the case of Example 1 in which the lithium ethoxide and the positive electrode active material were dissolved in ethanol and dried and fired, it was found that there was little difference in particle size when compared with Comparative Example 1. Therefore, it can be seen that both of Example 1 and Comparative Example 1 did not show a phenomenon in which positive electrode active materials were separately agglomerated.

Subsequently, FIGS. 5 (a) and 5 (b) are X-ray diffraction spectoscopy (XRD) result images, respectively, showing particle crystal structures of Example 1 and Comparative Example 1 of the present invention. In the case of XRD, it was analyzed for 1 hour and 11 minutes at 10 ^° to 80 ^° using D / Max-2200 / PC and 1 ^° per minute.

Referring to Figure 5, it can be seen the difference between the grain structure of Example 1 and Comparative Example 1. As shown in FIG. 5, it can be seen that in Example 1 and Comparative Example 1, peaks appear at the same point, and there are no new picks, so that there is no significant difference in the particle crystal structure. Even if the specific numerical values summarized in Table 4 are compared, it can be seen that the particle crystal structure of Example 1 prepared by treatment with lithium ethoxide has little change.

Particle size I ₍₀₀₃₎ I ₍₁₀₄₎ I ₍₀₀₃₎ / I ₍₁₀₄₎ Example 1 1575.4 1389.2 1.13 Comparative Example 1 1382.2 1267.3 1.09

6 is an image of FT-IR analysis result of Comparative Example 1 of the present invention. For FT-IR analysis, analysis was performed between 600 and 2000 nm using FT / IR0-4100.

Referring to FIG. 6, when comparing Example 1 and Comparative Example 1 through the results of FT-IR analysis, the peak of the carbonate in Example 1 is greater than Comparative Example 1. Through this, the presence of carbonate in Example 1 can be seen.

In addition, Table 5 below compares the presence of nitrogen (N), carbon (C), hydrogen (H), and sulfur (S) in Example 1 and Comparative Example 1 through Elemental analysis analysis. For this elemental analysis, Flash 2000 was used for analysis.

In particular, in Example 1, carbon (c) not shown in Comparative Example 1 was analyzed, which supports the carbonate concentration result of Table 2 and the presence of the carbonate pick of FT-IR in FIG. 6.

Example 1 (w%) Comparative Example 1 (w%) Nitrogen (N) - - Carbon (C) 0.597 - Hydrogen (H) - - Sulfur (S) - -

7 and 8 are SEM (Scanning electron microscopy) images of Comparative Example 1 and Example 1, respectively. Referring to FIG. 7, it can be seen that, unlike the clean surface of the positive electrode active material of Comparative Example 1, the coating layer was evenly distributed on the surface of the positive electrode active material treated with lithium ethoxide according to Example 1 of FIG. 8.

9 shows Comparative Example 1, FIGS. 10 and 11 show a transmission electron microscopy (TEM) image of Example 1 and an energy-dispersive X-ray spectroscopy (EDS) result image. In the case of TEM analysis, analysis was performed at an acceleration voltage of 160 kV using JEM-ARM300F (JEOL).

First, referring to FIG. 9, the surface and the interior of Comparative Example 1 can be analyzed. As a result of EDS analysis, it can be confirmed that the carbon pick does not float on the surface or the interior of Comparative Example 1. This means that the concentration of carbonate is low, as shown in Table 2 and Figure 6 above.

On the other hand, when the materials of the inside and the surface of the positive electrode active material of Example 1 were analyzed through the TEM images of FIGS. 10 and 11, carbon was found to the inside of the primary particles generated through EDS analysis. In particular, referring to FIG. 10, it can be confirmed that carbon (C) exists directly on the surface of the positive electrode active material. Therefore, it was confirmed through Tables 2 and 6 that in Example 1, unlike Comparative Example 1, a lot of carbonates exist, and the carbons appearing inside and on the surface of the primary particles of the positive electrode active material through the results shown in FIGS. It can be seen that it is a carbonate that is a lithium ion conductive material (especially oxide) of the present invention.

Evaluation Example 2: Composition evaluation

12A to 12C are XPS analysis images comparing carbon (C), lithium (Li), and oxygen (O) atomic ratios of Example 1 of the present invention, respectively. Referring to (a) to (c) of FIG. 7, it can be confirmed that amorphous carbons (C) are included in the positive electrode active material coated with the coating layer of Example 1 through CC bonding. In addition, it can be seen that lithium hydroxide (LiOH), lithium peroxide (Li ₂ O ₂ ), etc. are produced in addition to lithium carbonate (Li ₂ CO ₃ ) as a lithium ion conductive oxide. Therefore, Example 1 according to the present invention, as well as the amorphous carbon, lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium peroxide (Li ₂ O ₂ ), etc. It can be seen that plays a role in improving battery performance Can be.

13 is an X-ray diffraction analysis (XRD) result image of Example 1 of the present invention and lithium carbonate (Li ₂ CO ₃₎ included therein. Referring to FIG. 8, it can be seen that carbonate is generated when the lithium ethoxide is fired by treating the positive electrode active material.

Evaluation Example 3: Evaluation of initial charge / discharge and charge / discharge cycle characteristics

Test Methods

In the present invention, for the electrochemical evaluation of Example 1 and Comparative Example 1, an electrochemical cell (Premium Glass Co., Ltd) was used.

Half cell manufacturing and evaluation method

The composition of the positive electrode active material composite for the whole solid battery (half cell) included a positive electrode active material, a sulfide-based solid electrolyte, and a conductive material (Super-P) in a weight ratio of 69: 30: 1. The positive electrode active material composite is made into a pellet state by applying pressure in the half-cell manufacturing step, and the loading level according to the weight and area of the positive electrode composite is 20 mg / cm ² . Li / In composite was used as the negative electrode for the half cell.

For the production of such a half cell, first, a pressure of 10 MPa is applied to the sulfide-based solid electrolyte for 10 seconds to make pellets. After that, the positive electrode active material composite including the positive electrode active material on which the coating layer according to Example 1 is formed is placed on one side of the pellet, and then the negative electrode is placed on the opposite side. Thereafter, a pressure of 32 MPa was applied for 5 minutes to complete the cell. To evaluate the initial chemical conversion, the assembled cells were charged in a constant current (CC) mode up to 4.3V at 0.1C after a 4-hour rest process, and then discharged through CC mode at 0.1C up to 2.0V.

On the other hand, the half-cell electrochemical evaluation of Comparative Example 1 was previously conducted using the positive electrode active material composite containing the positive electrode active material of Comparative Example 1, in addition to not using the positive electrode active material having the coating layer of Example 1 formed (coated). The same procedure as in Example 1 was performed.

In the case of the discharge output evaluation, after charging to 4.3 V at 0.1 C in both Example 1 and Comparative Example 1, the cycle was repeated 3 cycles at 0.2 C, 0.5 C, 1 C, and 0.1 C again.

Full cell manufacturing and evaluation method

The electrochemical cell (Premium Glass Co., Ltd) was also used for the evaluation of the whole solid full cell battery of Example 1. In the case of the positive electrode active material composite electrode plate, the positive electrode active material with a coating layer, a sulfide-based solid electrolyte, a conductive material (Super-P), and a binder are composed of 68.2: 29.2: 1.33: 1.36. In the case of the negative electrode plate, the negative electrode active material, solid electrolyte, and binder are composed of 83: 14.7: 2.3. The loading level according to the weight and area of the positive electrode plate is 20.7 mg / cm ² , and the loading level according to the weight and area of the negative electrode plate is approximately 10.3 mg / cm ² . In the production of the entire solid full-cell battery, after the sulfide-based solid electrolyte layer is formed as in the half-cell fabrication, the positive electrode plate and the negative electrode plate are placed opposite to each other, and a pressure of 32 MPa is applied for 5 minutes to complete the cell. After the 4-hour rest process, the assembled cell was charged in 0.025C to 4.3V in constant current (CC) mode, and then charged in constant voltage (CV) mode to a current corresponding to 0.0125C. Then, discharge was performed in CC mode to 2.5V at 0.0125C.

On the other hand, in the case of the electrochemical evaluation of Comparative Example 1, in addition to not using the positive electrode active material formed (coated) of the coating layer of Example 1, using the positive electrode active material composite containing the positive electrode active material of Comparative Example 1, the previous Example The procedure was the same as in the evaluation method of 1.

Residual lithium measurement

After stirring the solution of 10 g of the positive electrode active material with the coating layer of Example 1 and de-ionized water (DIW) for 30 minutes at 350 rpm, the 40 g solution was filtered, and additionally 100 g of ultrapure water (DIW) After adding, it was measured using a potentiometric titrator (888 Titrando, Metrohm).

Residual lithium measurement of Comparative Example 1 was measured in the same manner except that the positive electrode active material on which the coating layer of Example 1 was formed was not used.

Evaluation results

FIG. 14 (a) shows a half cell including Example 1 and Comparative Example 1 of the present invention, and FIG. 15 shows initial charge / discharge characteristics for the full cell. 14B is an evaluation image showing the charge / discharge cycle characteristics of the half cell. Through the progress of the electrochemical evaluation of the entire solid battery, it can be confirmed that the difference in carbonate concentration and the increase in conductivity and the decrease in battery resistance when carbonate is present on the surface and inside of the positive electrode active material.

Referring to (a) of FIG. 14, the case of Example 1 shows a higher result in initial chemical conversion capacity and initial coulomb efficiency (see Table 6 below).

Initial Martian Capacity [mAh / g] Initial Coulomb Efficiency [%] Example 1 163 79.8 Comparative Example 1 155 81.7

Also, referring to (b) of FIG. 14, even in the half-cell discharge output test, the discharge capacity of Example 1 is higher than that of Comparative Example 1.

Subsequently, referring to FIG. 15, an effect difference of Example 1 and Comparative Example 1 was observed not only in half-cell evaluation but also in full-cell evaluation (see Table 7 below).

Initial Martian Capacity [mAh / g] Initial Coulomb Efficiency [%] Example 1 187 79.8 Comparative Example 1 182 81.7

That is, as in the half-cell results, Example 1 shows a higher result than Comparative Example 1 in the initial chemical conversion capacity. Thus, through half-cell evaluation and full-cell evaluation, when the carbonate is evenly present on the surface and inside of the positive electrode active material, reduction in cell resistance and improvement in conductivity are observed, and as a result, improvement in overall solid cell performance can be confirmed.

As a result, in the case of the positive electrode active material on which the coating layer according to the present invention is formed, lithium ions such as amorphous carbon (c), lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH) and lithium peroxide (Li ₂ O ₂ ) It can be seen that the conductive material (oxide) is evenly coated on the surface and inside of the positive electrode active material. In addition, unlike conventional, even when the concentration of carbonate is high, lithium ion conductive materials such as amorphous carbon (c), lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH) and lithium peroxide (Li ₂ O ₂ ) When (oxide) is evenly coated on the surface and inside of the positive electrode active material, it can be seen that it shows a decrease in battery resistance and an improvement in conductivity. In the case of the positive electrode active material having the coating layer formed (coated) as described above, it shows higher overall solid cell performance and efficiency than the conventional positive electrode active material. In addition, it was confirmed that the discharge output is greatly improved than the existing positive electrode active material, and the capacity recovery rate is also improved.

In the above, preferred embodiments of the present invention have been illustrated and described, but the present invention is not limited to the above-described specific embodiments, and the technical field to which the present invention pertains without departing from the gist of the present invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical idea or prospect of the present invention.

10: positive electrode active material 30: coating layer

Claims (17)

As a positive electrode active material with a coating layer formed on the surface and inside,
The coating layer includes lithium (Li) ion conductive oxide and amorphous carbon (C),
The lithium-ion conductive oxide, carbonate (CO ₃ ^-) a positive electrode active material comprising a. According to claim 1,
The concentration of the carbonate is 5000 ppm to 16000 ppm of the positive electrode active material. According to claim 1,
The concentration of the carbonate is 10000 ppm to 16000 ppm of the positive electrode active material. According to claim 1,
A positive electrode active material containing the amorphous carbon in 0.2 w% to 1.0 w%. According to claim 1,
The lithium ion conductive oxide is a positive electrode active material selected from the group consisting of lithium carbonate (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium peroxide (Li ₂ O ₂ ), and combinations thereof. Preparing a positive electrode active material;
Forming a mixture by adding a lithium (Li) -containing precursor to the positive electrode active material; And
Comprising the step of calcination (calcination) the mixture,
The step of calcining the mixture includes forming a coating layer containing a lithium ion conductive oxide derived from the lithium-containing precursor,
Method for manufacturing a positive electrode active material with a coating layer formed. The method of claim 6,
In the step of forming the mixture,
With respect to 100 parts by weight of the positive electrode active material, the lithium-containing precursor is added in an amount of 0.1 to 5 parts by weight, a method for producing a positive electrode active material with a coating layer. The method of claim 6,
In the step of forming the mixture,
The lithium-containing precursor is a method for producing a positive electrode active material containing lithium ethoxide (CH ₃ CH ₂ OLi). The method of claim 6,
The step of firing the mixture,
Nitrogen (N ₂ ), oxygen (O ₂ ), argon (Ar), air (Air), and a method for producing a positive electrode active material with a coating layer formed, which is performed under a gas atmosphere selected from the group consisting of these. The method of claim 6,
The step of firing the mixture,
Method of producing a positive electrode active material is formed at a temperature of 300 ℃ to 500 ℃, the coating layer is formed. The method of claim 6,
The step of firing the mixture,
A method for producing a positive electrode active material on which a coating layer is formed, which is performed for 1 hour to 4 hours. The method of claim 6,
The lithium-ion conductive oxide, carbonate (CO ₃ ^-), method for producing a positive electrode active material coating layer is formed comprising a. The method of claim 12,
The carbonate is contained in a concentration of 5000 ppm to 16000 ppm, a method of manufacturing a positive electrode active material with a coating layer is formed. The method of claim 12,
The carbonate is contained in a concentration of 10000 ppm to 16000 ppm, a method for producing a positive electrode active material with a coating layer. The method of claim 6,
The coating layer further comprises amorphous carbon (C),
A method for producing a positive electrode active material having a coating layer, comprising 0.2 w% to 1.0 w% of the amorphous carbon. The method of claim 6,
The lithium ion conductive oxide is selected from the group consisting of lithium tansium (Li ₂ CO ₃ ), lithium hydroxide (LiOH), lithium peroxide (Li ₂ O ₂ ), and combinations thereof, a method for producing a positive electrode active material with a coating layer . A positive electrode active material having a coating layer formed by the method of any one of claims 6 to 16.

Images