WO2020059902A1 - Cathode material having silicon oxide coating layer formed thereon, cathode comprising same, sodium ion battery, and manufacturing method therefor - Google Patents

Abstract

The present invention relates to: a cathode material having a silicon oxide coating layer formed thereon, capable of improving the battery characteristics of a sodium ion battery; a cathode and a sodium ion battery, both of which comprise same; and a manufacturing method therefor. The present invention provides a cathode material for a sodium ion battery, comprising: a metal oxide having an O₃ layered structure represented by Na_1-xMeO₂ (Me is Ni, Fe and Mn, and 0<x<1); and a silicon oxide coating layer formed by coating silicon oxide on the surface of the metal oxide.

Description

Anode material on which silicon oxide coating layer is formed, anode and sodium ion battery containing the same, and method for manufacturing same

The present invention relates to a sodium ion battery and a method for manufacturing the same, and more specifically, a positive electrode material having a silicon oxide coating layer on which the silicon oxide is coated on the surface of the positive electrode material to improve battery characteristics, the positive electrode and the sodium ion battery comprising the same, and It relates to a manufacturing method.

As the demand of consumers changes due to the digitization and high performance of electronic products, the market demand is changing with the development of batteries with high capacity due to thin, light weight and high energy density. In addition, the development of hybrid electric vehicles, electric vehicles, and fuel cell vehicles has been actively progressed in order to cope with future energy and environmental problems.

Lithium secondary batteries have been put into practical use as batteries that can be charged and discharged in a compact, lightweight and high capacity, and are used in portable electronic and communication devices such as small video cameras, mobile phones, and notebook computers. The lithium secondary battery is composed of a positive electrode, a negative electrode, and an electrolyte, and it charges and discharges because lithium ions from the positive electrode material are inserted into the negative electrode material by charging and resorption when discharged. This is possible.

Meanwhile, in recent years, research on a sodium-based secondary battery (hereinafter referred to as “sodium ion battery”) using sodium instead of lithium has been reexamined. Since sodium has a rich resource reserve, if a secondary battery using sodium instead of lithium can be manufactured, the secondary battery can be manufactured at a low cost.

For the commercialization of sodium ion batteries, research on positive electrode materials, which are important materials, is being actively conducted. Among the anode materials, a metal oxide having a layered structure Na _{1 - x} MeO ₂ (Me = Mn, Fe, Co, Ni, etc.) is attracting attention as a cathode material having high commercialization potential.

Among these positive electrode materials, the Ni-Fe-Mn-based positive electrode material that does not contain expensive Co has an O ₃ structure and is known to be capable of securing a high reversible capacity. However, the Ni-Fe-Mn-based positive electrode material has a disadvantage in that battery characteristics related to output and life characteristics are significantly reduced.

[Advanced technical literature]

[Patent Document]

Published Patent Publication No. 2017-0098529 (released on August 30, 2017)

The disadvantage of the Ni-Fe-Mn-based positive electrode material is that a sodium residue is present on the surface of the positive electrode material, and when exposed to the atmosphere, the amount is significantly increased, thereby acting as a factor that deteriorates battery characteristics.

Accordingly, an object of the present invention is to reduce the resistance by surface by-products such as sodium residue through surface modification of the positive electrode material to secure a stable lifespan characteristic, thereby forming a positive electrode material having a silicon oxide coating layer capable of improving battery characteristics, and a positive electrode comprising the same. And a sodium ion battery and a method for manufacturing the same.

In order to achieve the above object, the present invention provides a positive electrode material having a silicon oxide coating layer formed on its surface, a positive electrode and a sodium ion battery comprising the same, and a method for manufacturing the same.

The present invention Na _{1 - x} MeO ₂ (Me = Ni, Fe and Mn, a metal oxide having an O ₃ layered structure represented by 0 <x <1); And a silicon oxide coating layer coated with silicon oxide on the surface of the metal oxide.

The metal oxide may be represented by Na _{1 - x} Ni _a Fe _b Mn _c O ₂ (a + b + c = 1).

The present invention also provides Na _{1 - x} MeO ₂ (Me = Ni, Fe and Mn, preparing a metal oxide having an O ₃ layered structure represented by 0 <x <1); And coating the surface of the metal oxide with silicon oxide to form a silicon oxide coating layer.

The forming step may include adding tetraethyl orthosilicate (TEOS) to the metal oxide; Converting the TEOS into silicon oxide by heat treatment; And forming the silicon oxide coating layer by coating the silicon oxide on the surface of the metal oxide.

In the introducing step, the TEOS 0.5 to 5 wt% may be added to the metal oxide 95 to 99.5 wt%.

The present invention also provides a positive electrode for a sodium ion battery comprising the positive electrode material.

And the present invention provides a sodium ion battery comprising the positive electrode.

According to the present invention, by forming a silicon oxide coating layer on the surface of the metal oxide having the O ₃ layered structure, reducing the resistance by surface by-products such as sodium residue that may be present on the surface of the anode material to secure a stable life characteristics Battery characteristics can be improved.

1 is a flow chart according to a method of manufacturing a positive electrode material for a sodium ion battery according to the present invention.

FIG. 2 is a detailed flow chart showing the steps of forming the silicon oxide coating layer of FIG. 1.

3 is a photograph showing a cathode material for a sodium ion battery according to a comparative example.

4 is a photograph showing a cathode material for a sodium ion battery according to an embodiment.

5 is a photograph showing the results of SEM-EDS analysis of the positive electrode material for a sodium ion battery according to the embodiment.

6 is a graph showing charge and discharge characteristics of a sodium ion battery using a cathode material according to Comparative Examples and Examples.

7 is a graph showing output characteristics of a sodium ion battery using a positive electrode material according to Comparative Examples and Examples.

8 is a graph showing the life characteristics of a sodium ion battery using a cathode material according to Comparative Examples and Examples.

It should be noted that in the following description, only parts necessary for understanding the embodiments of the present invention are described, and descriptions of other parts will be omitted without detracting from the gist of the present invention.

The terms or words used in the present specification and claims described below should not be construed as being limited to ordinary or dictionary meanings, and the inventor is appropriate as a concept of terms to describe his or her invention in the best way. It should be interpreted as a meaning and a concept consistent with the technical idea of the present invention based on the principle that it can be defined as such. Therefore, the configuration shown in the embodiments and drawings described in this specification is only a preferred embodiment of the present invention, and does not represent all of the technical spirit of the present invention, and various equivalents that can replace them at the time of this application It should be understood that there may be and variations.

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

1 is a flow chart according to a method of manufacturing a positive electrode material for a sodium ion battery according to the present invention. FIG. 2 is a detailed flow chart showing the steps of forming the silicon oxide coating layer of FIG. 1.

1 and 2, a method of manufacturing a cathode material for a sodium ion battery according to the present invention provides a layered structure represented by Na _{1 - x} MeO ₂ (Me = Ni, Fe and Mn, 0 <x <1). It includes a step of preparing a metal oxide having (S10), and forming a silicon oxide coating layer by coating the surface of the metal oxide with silicon oxide (S30).

Step S10 will be described in detail as follows. In step S10, the metal oxide is manufactured in powder form.

First, a precursor mixture is prepared by mixing a metal oxide precursor represented by (Me) OH ₂ (Me = Ni, Fe and Mn) and a sodium precursor containing Na ₂ CO ₃ .

Then, the precursor mixture is fired to prepare a metal oxide having an O ₃ layered structure. At this time, the firing may be performed at 760 to 960 ° C for 14 to 34 hours.

At this time, the input amount of Na ₂ CO ₃ may be adjusted so that the sodium content of the metal oxide is less than one.

The metal oxide prepared in step S10 is in the form of a powder, Na _{1 - x} MeO ₂ O ₃ layer has an offset structure represented by (Me = Ni, Fe and Mn , 0 <x <1).

Step S30 will be described in detail as follows.

First, in step S31, tetraethyl orthosilicate (TEOS) is added to the metal oxide. That is, 0.5 to 5 wt% of TEOS is added to 95 to 99.5 wt% of metal oxide. TEOS is converted to silicon oxide through heat treatment.

At this time, step S31 proceeds as a solution process, and after preparing a mixed solution in which metal oxide and TEOS are added, the mixture is stirred for a certain time at room temperature so that the metal oxide and TEOS can be uniformly mixed. Then, the mixture is filtered and dried to remove the solvent, whereby TEOS adsorbed powder can be obtained on the surface of the metal oxide.

Then, after converting TEOS in step S33 to silicon oxide by heat treatment, in step S35, the silicon oxide is coated on the surface of the metal oxide to form a silicon oxide coating layer. That is, the TEOS adsorbed on the surface of the metal oxide is converted into silicon oxide and formed into a silicon oxide coating layer by putting the powder adsorbed on the surface of the metal oxide into the heat treatment facility and then heat treating it in an air atmosphere.

In order to confirm the electrochemical properties of the positive electrode material produced by the manufacturing method of the present invention, a positive electrode material according to Examples and Comparative Examples was prepared as follows.

The positive electrode material according to the comparative example is Na ₀ having a Na content of 0.9 _{. 9} (Ni _0.25 Fe _0.25 Mn _0.5 ) O ₂ was used. Synthesis of positive electrode material according to a comparative example was prepared by precursor _{(Ni 0. 25 Fe 0.} 25 Mn 0. 5) After mixing ratio quantitative with OH ₂ and Na ₂ CO _3, 24 sigan baked at 860 ℃.

The positive electrode material according to the embodiment was prepared by additionally performing a process of forming a silicon oxide coating layer as follows for the positive electrode material according to the comparative example.

First, 1 wt% of TEOS was added to 70 mL of absolute ethanol to the weight of the metal oxide, followed by stirring for about 10 minutes to prepare a coating solution. After stirring the prepared coating solution for 1 hour at room temperature, the solvent was dried at 80 degrees after filtering to prepare a powder with TEOS adsorbed on the surface of the metal oxide.

Then, the powder adsorbed on the surface of the metal oxide was heat-treated in a tube electric furnace to prepare a positive electrode material according to an embodiment. At this time, the heat treatment was performed in an air atmosphere at 700 degrees for 4 hours. In the heat treatment process, TEOS adsorbed on the surface of the metal oxide is converted to silicon oxide to form a silicon oxide coating layer.

To evaluate the electrochemical properties of a sodium ion battery using a cathode material according to Examples and Comparative Examples, CR2032 coin cells were prepared. At this time, Na: metal as the cathode, glass fiber (glass fiber) as the separator, and electrolyte: 1 M of NaClO ₄ dissolved in EC: PC (1: 1) was used.

3 is a photograph showing a cathode material for a sodium ion battery according to a comparative example. 4 is a photograph showing a cathode material for a sodium ion battery according to an embodiment. 3 and 4 are SEM pictures, and (b) is an enlarged picture of (a).

3 and 4, when comparing the positive electrode material according to the embodiment with the positive electrode material according to the comparative example, it was confirmed that a silicon oxide coating layer was formed on the surface of the positive electrode material according to the embodiment.

5 is a photograph showing the results of SEM-EDS analysis of the positive electrode material for a sodium ion battery according to the embodiment.

5, it can be seen that the positive electrode material according to the embodiment includes Na, Ni, Fe, Mn, and Si, and Si is uniformly distributed on the surface of the positive electrode material.

That is, the positive electrode material according to the embodiment can be confirmed that a silicon oxide coating layer of a silicon oxide material is formed on the surface.

6 is a graph showing charge and discharge characteristics of a sodium ion battery using a cathode material according to Comparative Examples and Examples.

Referring to FIG. 6, it can be seen from the graph evaluating the charge / discharge characteristics at 0.1C that the overvoltage of the sodium ion battery using the positive electrode material according to the embodiment is improved.

Therefore, although the discharge capacity of the sodium ion battery according to the comparative example is 161 mAh / g, it can be seen that the discharge capacity of the sodium ion battery according to the embodiment is improved to 175 mAh / g.

Table 1 is a measurement value of the output characteristics at 0.1C to 5C of a sodium ion battery using a cathode material according to Comparative Examples and Examples. In Table 1, Na 0.9. Represents a comparative example, and H.TEOS represents an example.

7 is a graph showing output characteristics of a sodium ion battery using a positive electrode material according to Comparative Examples and Examples.

Referring to Table 1 and Figure 7, it can be seen that the embodiment shows excellent output characteristics. In particular, looking at the discharge curve, it can be seen that the overvoltage of the sodium ion battery according to the embodiment is significantly improved and the capacity is increased. This means that the sodium ion battery according to the embodiment exhibits better properties in terms of energy density (Wh).

Table 2 is a value obtained by measuring the capacity retention rate after one, 50, and 100 cycles of the sodium ion battery using the positive electrode material according to Comparative Examples and Examples. At this time, the evaluation was performed at room temperature cycle characteristics at 0.5C to confirm whether the life was improved.

8 is a graph showing the life characteristics of a sodium ion battery using a cathode material according to Comparative Examples and Examples.

Referring to Table 2 and Figure 8, comparing the capacity retention rate after 100 cycles, it can be seen that the comparative example is 82%, and the example is 88%, which improves the lifespan characteristics with a silicon oxide coating.

As described above, in the present invention, by forming a silicon oxide coating layer on the surface of a metal oxide having an O ₃ layered structure, the resistance by surface by-products such as sodium residues that may be present on the surface of the anode material is reduced, through which the sodium ion battery It is possible to improve the battery characteristics by securing the stable life characteristics of.

On the other hand, the embodiments disclosed in the specification and the drawings are merely presented as specific examples for ease of understanding, and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

Claims (10)

Na _{1 - x} MeO ₂ (Me = Ni, Fe and Mn, a metal oxide having an O ₃ layered structure represented by 0 <x <1); And A silicon oxide coating layer coated with silicon oxide on the surface of the metal oxide; A cathode material for a sodium ion battery comprising a. According to claim 1, The metal oxide is Na _{1 - x} Ni _a Fe _b Mn _c O ₂ (a + b + c = 1) is a cathode material for a sodium ion battery, characterized in that represented by. Na _{1 - x} MeO ₂ (Me = Ni, Fe and Mn, preparing a metal oxide having an O ₃ layered structure represented by 0 <x <1); And Forming a silicon oxide coating layer by coating with silicon oxide on the surface of the metal oxide; Method for producing a positive electrode material for a sodium ion battery comprising a. According to claim 3, In the preparing step, The metal oxide is Na _{1 - x} Ni _a Fe _b Mn _c O ₂ (a + b + c = 1) Method for producing a cathode material for a sodium ion battery, characterized in that. According to claim 4, In the forming step, Adding tetraethyl orthosilicate (TEOS) to the metal oxide; Converting the TEOS into silicon oxide by heat treatment; And Forming a silicon oxide coating layer by coating the silicon oxide on the surface of the metal oxide; Method for producing a cathode material for a sodium ion battery comprising a. The method of claim 5, In the step of injecting, Method of manufacturing a positive electrode material for a sodium ion battery, characterized in that the TEOS 0.5 to 5 wt% is added to the metal oxide 95 to 99.5 wt%. Na _{1 - x} MeO ₂ (Me = Ni, Fe and Mn, 0 <x <1) represented by a metal oxide having an O ₃ layered structure, and a positive electrode material comprising a silicon oxide coating layer coated with a silicon oxide on the surface of the metal oxide Anode for sodium ion batteries. The method of claim 7, The metal oxide is a Na _{1 - x} Ni _a Fe _b Mn _c O ₂ (a + b + c = 1) is a positive electrode for a sodium ion battery. Na _{1 - x} MeO ₂ (Me = Ni, Fe and Mn, containing a metal oxide having a layer structure of O ₃ represented by 0 <x <1), and a positive electrode material having a silicon oxide coating layer coated with a silicon oxide on the surface of the metal oxide Sodium ion battery comprising a positive electrode. The method of claim 9, The metal oxide is sodium ion battery, characterized in that represented by Na _{1 - x} Ni _a Fe _b Mn _c O ₂ (a + b + c = 1).

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