KR20230032241A - Method for manufacturing pre-potassiated carbon, conducting agents or electrode materials for potassium-ion secondary battery manufactured thereby and potassium-ion secondary battery including the same - Google Patents

Abstract

The present invention relates to a method for producing pre-potassiated carbon, comprising the steps of: (a) preparing a mixed powder of potassium (K) and carbon (C); and (b) applying mechanical energy to the mixed powder to produce pre-potassiated carbon using a non-electrochemical pre-potassiation reaction. According to the method for producing pre-potassiated carbon according to the present invention, pre-potassiated carbon can be manufactured simply and efficiently using ball milling, a simple solid synthesis method, without going through complicated and inefficient processes such as chemical methods. In addition, when pre-potassiated carbon prepared by the above method is used as an electrode conductive material or electrode active material for a potassium ion secondary battery, it is possible to implement a potassium ion secondary battery system with high capacity and excellent cycle life by maintaining high capacity and excellent initial efficiency.

Description

Method for producing pre-potassiumized carbon, conductive material or electrode material for secondary battery produced thereby, and potassium ion secondary battery including the same AND POTASSIUM-ION SECONDARY BATTERY INCLUDING THE SAME}

The present invention uses a non-electrochemical pre-potassiation reaction of potassium (K) metal and carbon (C) to obtain pre-potassied carbon that can be used as an electrode conductive material or an electrode active material. It relates to a manufacturing method, a potassium ion secondary battery electrode conductive material or electrode active material comprising the pre-potassiumized carbon produced thereby, and a potassium ion secondary battery comprising the same.

A secondary battery is a battery that can be used repeatedly through a charging process in the opposite direction to a discharge process in which chemical energy is converted into electrical energy. Recently, with the commercialization of portable electronic products and electric vehicles, the demand for secondary batteries is rapidly increasing. .

Currently, lithium ion secondary batteries are mainly used as commercially available secondary batteries, but due to limited reserves of lithium, which is a main raw material, the price is expensive and is not sufficient to meet the demand for secondary batteries.

Therefore, the development of a new secondary battery that can replace the lithium ion secondary battery is required, and recently, research and development on a potassium ion secondary battery using potassium instead of lithium has been actively attempted.

Potassium reserves are about 8 times more abundant than lithium and the price is 1/10 cheaper. Using potassium instead of lithium makes it more economical by replacing copper with aluminum as the current collector material of the anode, and potassium ion secondary batteries are lithium ion Since the manufacturing process of the secondary battery is followed as it is, there is no need to newly equip manufacturing facilities, manufacturing cost can be reduced, and load characteristics can be improved compared to lithium ion secondary batteries.

However, potassium is chemically active and has safety problems such as reacting violently with water. When potassium metal is used as an electrode, the growth of potassium dendrites occurs due to battery operation, resulting in a short circuit of the battery. Occurs.

On the other hand, carbon black, which is widely used as an electrode conductive material for conventional lithium-ion secondary batteries and is inexpensive, can react with potassium electrochemically, but due to its high initial irreversibility, carbon black itself is not suitable for application as an electrode material for potassium-ion secondary batteries. There is a group.

Japanese Unexamined Patent Publication No. 2021-104921 (Publication date: 2021.07.26) Japanese Patent Registration No. 6845507 (registration date: 2015.04.29)

An object of the present invention is to use a new electrode conductive material or electrode active material for a potassium ion secondary battery that exhibits excellent charge/discharge characteristics and initial efficiency using a simple and efficient method without going through complicated and inefficient processes such as conventional chemical methods. It is to provide a method for non-electrochemically producing possible carbon-based materials.

Another object of the present invention is to provide a novel electrode conductive material or electrode active material for a potassium ion secondary battery prepared by the above method, and further, to provide a potassium ion secondary battery including the same.

The present invention for solving the above problems, (a) preparing a mixed powder of potassium (K) and carbon (C); And (b) applying mechanical energy to the mixed powder to cause a pre-potassiation reaction to produce pre-potassied carbon. provides a way

In addition, the carbon is at least one selected from the group consisting of graphite-based carbon, carbon black-based carbon, activated carbon-based carbon, hard carbon, soft carbon, and carbon nanostructures. It provides a method for producing pre-potassied carbon.

In addition, in step (b), a high-energy spex mill, a vibrotary-mill, a Z-mill, a planetary ball-mill or an attrition mill ( It provides a method for producing pre-potassiumized carbon, characterized in that by applying mechanical energy to the attrition-mill).

In addition, it provides a method for producing all-potassiumized carbon, characterized in that for producing all-potassiumized carbon represented by K _x C (X = 0.01 ~ 1) in the step (b).

In addition, it provides a method for producing pre-potassiumized carbon, characterized in that for producing a pre-potassiumized carbon powder having an average diameter of 1 nm or more and 500 μm or less in the step (b).

In addition, the present invention provides an electrode conductive material or electrode active material for a potassium ion secondary battery including pre-potassied carbon prepared by the above manufacturing method in another aspect of the invention.

In addition, the present invention provides a potassium ion secondary battery including the electrode conductive material or electrode active material for the potassium ion secondary battery in another aspect of the invention.

According to the method for producing pre-potassinated carbon according to the present invention, it is pre-potassied simply and efficiently using ball milling, a simple solid synthesis method, without going through complicated and inefficient processes such as chemical methods. Carbon (pre-potassied carbon) can be produced.

In addition, when the pre-potassinated carbon prepared by the above method is used as an electrode conductive material or an electrode active material of a potassium ion secondary battery, potassium ions having excellent cycle life while maintaining high initial efficiency and capacity A secondary battery system may be implemented.

1 is a process flow chart sequentially describing each step of a method for producing pre-potassinated carbon according to the present invention.
2 is a conceptual diagram for explaining a method for producing pre-potassied carbon according to an embodiment of the present invention.
3 is a schematic diagram of a potassium ion secondary battery including pre-potassied carbon as an electrode active material according to the present invention.
4 is a schematic diagram of a potassium ion secondary battery negative electrode including pre-potassinated carbon as an electrode active material according to the present invention.
5 is a graph showing the results of X-ray diffraction analysis of pre-potassinated carbon.
6 is an electron energy loss spectroscopy (EELS) graph of pre-potassinated carbon.
7 is a high-resolution transmission electron microscope (HR-TEM) photograph of the pre-potassinated carbon prepared above.
8A is a graph showing the results of a charge/discharge experiment when pre-potassinated carbon is used as an electrode for a potassium ion secondary battery.
8B is a chart comparing initial capacity and initial efficiency when graphite, amorphous carbon, and pre-potassiumized carbon are used as electrodes for a potassium ion secondary battery.
9 is a graph showing cycle characteristic data when pre-potassinated carbon is used as an anode active material in a potassium secondary battery.

In describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Embodiments according to the concept of the present invention can be applied with various changes and can have various forms, so specific embodiments are illustrated in the drawings and described in detail in this specification or application. However, this is not intended to limit the embodiments according to the concept of the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, or substitutes included in the spirit and technical scope of the present invention.

Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise" or "having" are intended to designate that the described feature, number, step, operation, component, part, or combination thereof exists, but one or more other features or numbers However, it should be understood that it does not preclude the presence or addition of steps, operations, components, parts, or combinations thereof.

Hereinafter, the present invention will be described in detail.

As shown in FIG. 1, the method for producing pre-potassinated carbon according to the present invention includes the steps of (a) preparing a mixed powder of potassium (K) and carbon (C); and (b) applying mechanical energy to the mixed powder to produce pre-potassied carbon using a pre-potassiation reaction.

In the step (a), a mixed powder is prepared by mixing potassium (K) and carbon (C) powder, which are starting raw materials for compound production, and the method used for preparing the mixed powder in this step is potassium ( K) and carbon (C) powder is not particularly limited as long as it is a method capable of uniformly mixing.

The potassium (K) used in the preparation of the mixed powder in this step may be not only metallic potassium in powder form, but also potassium in the form of a foil, agglomerate, etc., which is refined through grinding or the like. , when using potassium in the form of a metal piece, its size is preferably less than 1 cm ² .

In addition, the carbon-based material constituting the carbon powder introduced in this step (a) is not particularly limited in its type, but graphite-based carbon such as natural graphite, artificial graphite, expanded graphite and graphene; Super P, Super C, Acetylene black, Denka black, Ketjen black, Channel black, Furnace black, Thermal Carbon black-based carbon such as thermal black, contact black, and lamp black; Active carbon (Active carbon)-based carbon; carbon nanostructures such as carbon fibers, carbon nanotubes (CNTs), fullerenes, and graphene; hard carbon; And it may be one or a combination of two or more selected from soft carbon and the like.

In this step (a), the carbon powder is preferably added in an amount of 96.8 wt% to 23.5 wt% based on the total weight of the mixed powder. When the carbon powder is included in less than 23.5 wt%, the amount of potassium metal becomes excessive in the total weight, and it is not preferable to prepare pre-potassied carbon in step (b) to be described later.

Next, in the step (b), the mechanical energy obtained in the previous step is applied to cause a pre-potassiation reaction between potassium (K) and carbon (C) to produce pre-potassied carbon. It is a step of manufacturing.

Figure 2 is a conceptual diagram for explaining a method for producing pre-potassied carbon in this step (b).

Referring to FIG. 2, mechanical energy is applied to a mixed powder containing potassium (K) and carbon (C) powder by high energy mechanical milling (HEMM), and potassium (K) and carbon (C) powder are applied. ) causes a partial pre-potassiation reaction of the liver to obtain pre-potassinated carbon, and this process can be expressed by the reaction equation below.

<reaction formula>

xK + C → K _x C (X=0.01 ~ 1)

Referring to the above reaction scheme, by a solid synthesis method using ball milling, potassium (K) metal and carbon may be added to induce a pre-potassium reaction to prepare all-potassiumized carbon. In particular, by using a ball milling method of a simple process to induce a pre-potassium reaction, the composite can be simply and efficiently prepared without performing a conventional chemical synthesis method.

The pre-potassiumized carbon has a high initial efficiency in the initial charge and discharge process when it is applied to a potassium ion secondary battery because the carbon contains some potassium before application to the secondary battery, which is amorphous, that is, amorphous carbon It can solve the biggest problem of initial efficiency, and furthermore, it can solve the limitation of the negative electrode capacity of potassium ion secondary battery with a higher reversible capacity than graphite currently commercially available.

In this step (b), the method of applying mechanical energy to the pre-potassiated carbon powder is not particularly limited, but it is recommended to use high-energy ball milling for the pre-potassiation reaction. desirable.

For reference, high-energy ball milling can induce chemical reactions in reactants through maximized diffusivity between powder particles as well as atomization of powder by applying high energy through high torque to reactants.

The high-energy ball milling includes a high-energy spex mill, a vibrotary-mill, a Z-mill, a planetary ball-mill, and an attrition-mill. mill) can be performed by all known ball milling devices used for high-energy ball milling. For reference, in a typical high-energy ball milling process, the temperature may rise to 200° C. and the pressure may be on the order of 6 GPa during ball milling.

As described above, if the solid-state synthesis method using high-energy ball milling is used, pre-potassinated carbon can be simply and efficiently produced without performing a conventional chemical synthesis method. Meanwhile, a more specific method for preparing pre-potassinated carbon according to the present invention through a solid phase synthesis method using high energy ball milling is as follows.

First, uniformly mixed potassium metal pieces and carbon component powders are loaded into a cylindrical vial together with balls, mounted in a high-energy ball mill, and mechanical synthesis is performed at a rotation speed of 500-2000 times per minute to obtain pre-potassiumized carbon. manufacture The ball milling may be performed for 1-24 hours. Here, the weight ratio of the ball and the mixture is maintained at, for example, 10: 1 to 30: 1, and mechanical synthesis is prepared in an argon gas atmosphere glove box to minimize the influence of oxygen and moisture.

Pre-potassinated carbon prepared by the above-described manufacturing method, particularly pre-potassinated carbon including amorphous carbon, has improved initial efficiency and charging and discharging characteristics. Therefore, it is suitable for use as an electrode active material for secondary batteries, especially potassium ion secondary batteries. In particular, the cycle life of the secondary battery including the pre-potassinated carbon is also very excellent.

On the other hand, the pre-potassium carbon is preferably in the form of a powder containing 96.8 wt% to 23.5 wt% of carbon and having an average diameter of 1 nm or more and less than 500 μm, and is preferably an amorphous carbon particle.

In addition, the present invention provides an electrode conductive material or electrode active material for a potassium ion secondary battery including pre-potassied carbon prepared by the above manufacturing method in another aspect of the invention.

In addition, the present invention provides a potassium ion secondary battery including the electrode conductive material or electrode active material for the potassium ion secondary battery in another aspect of the invention.

3 is a schematic diagram of a potassium ion secondary battery including pre-potassied carbon as an electrode active material according to the present invention.

The secondary battery 1 may include a positive electrode 12 , a negative electrode 11 , and a separator 13 disposed between the positive electrode 12 and the negative electrode 11 . The secondary battery 1 may further include an electrolyte (not shown), a battery container 14, and a sealing member 15 for sealing the battery container 14. The secondary battery 1 may be manufactured by sequentially stacking the positive electrode 12 , the negative electrode 11 , and the separator 13 and then storing the battery container 14 in a wound state.

4 is a schematic diagram of a potassium ion secondary battery negative electrode including pre-potassinated carbon as an electrode active material according to the present invention.

The negative electrode 11 may include a current collector 111 and an active material layer 112 formed on the current collector 111 . The active material layer 112 includes pre-potassied carbon according to the present invention. The anode 11 is a water-insoluble binder such as polyvinylidene fluoride (PVdF) or polyethyleneimine, polyaniline, polythiophene, polyacrylic acid (PAA), carboxymethylcellulose (CMC), styrene-butadiene lever (SBR) A water-soluble binder such as may be further included.

Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content will be thorough and complete, and the spirit of the present invention will be sufficiently conveyed to those skilled in the art.

<Example>

(1) Preparation of pre-potassied carbon through pre-potassiation of potassium metal and carbon

After mixing a piece of potassium foil with a size of less than 1 cm ² and carbon (Super P) powder at a molar ratio of 0.2:1, a 3/8-inch 3/8-inch vial was placed in a cylindrical vial made of SKD11 with a diameter of 5.5 cm and a height of 9 cm. After being charged with balls and attached to a ball mill (vibrating mill, spex 8000), mechanical synthesis was performed at a rotational speed of 900 times per minute.

At this time, the weight ratio between the ball and the powder was maintained at 20:1, and mechanical synthesis was prepared in an argon gas atmosphere glove box in order to suppress the influence of oxygen and moisture as much as possible. The mechanical synthesis was performed for 3 hours to prepare pre-potassinated carbon.

The prepared pre-potassinated carbon can be synthesized as K _x C (X = 0.01 ~ 1) by the molar ratio of potassium, and the pre-potassied carbon is converted to potassium secondary When used as an electrode material for a battery, higher capacity and initial efficiency than graphite can be realized by overcoming the problems of low reversible capacity and initial efficiency, which are disadvantages of a typical carbon-based negative electrode (graphite). Materials used in one embodiment of this study are used by preparing potassium metal and carbon powder together in an appropriate molar ratio in order to manufacture pre-potassied carbon containing potassium and carbon components.

5 is a graph showing the results of X-ray diffraction analysis of pre-potassinated carbon. The prepared pre-potassinated carbon did not show a peak related to the bonding between potassium and carbon, and showed the result of X-ray diffraction analysis of an amorphous material.

6 is an electron energy loss spectroscopy (EELS) graph of pre-potassinated carbon. In the pre-potassinated carbon produced, π* and σ* bonds, which are inherent bonds of carbon-based materials, appeared at 286 and 293 eV, respectively, in the energy range of 270 to 360 eV, and L ₃ of potassium , bonds corresponding to the L ₂ -edge appeared at 298 and 300 eV, respectively. In addition, it can be seen that a specific bond between potassium and carbon exists in the pre-potassinated carbon prepared through the KC bonding peak appearing at 289 eV.

7 is a high-resolution transmission electron microscope (HR-TEM) photograph of the pre-potassinated carbon prepared above. Referring to FIG. 7 , it can be confirmed that amorphous pre-potassinated carbon was manufactured through the above manufacturing method, and the pre-potassied carbon manufactured through the EDS mapping picture is potassium And it can be seen that it is uniformly distributed with the carbon component.

(2) Evaluation of initial efficiency characteristics and cycle characteristics of a potassium ion secondary battery containing pre-potassinated carbon.

8A is a graph showing the results of a charge/discharge experiment when pre-potassinated carbon is used as an electrode for a potassium ion secondary battery. The blue graph of FIG. 8A shows the charging and discharging results of carbon (amorphous carbon) subjected to only ball milling under the same conditions as pre-potassied carbon, which is an embodiment of the present invention. The red graph of FIG. 8A is a graph showing charge and discharge behaviors for the first cycle in the case of using pre-potassinated carbon. The charge and discharge capacities of the first cycle were 336 mAh/g and 406 mAh/g, and the efficiency of the initial cycle was about 120.7%. This shows improved results compared to the charge and discharge capacities of 490 mAh/g and 175 mAh/g, and the efficiency of the initial cycle of 35.7% of the amorphous carbon prepared by the same method.

FIG. 8B is a graph comparing initial capacity and initial efficiency when graphite, amorphous carbon, and all-potassiumized carbon are used as electrodes for a potassium ion secondary battery. The prepared pre-potassinated carbon showed significantly higher capacity and initial efficiency than graphite, a conventional carbon-based anode material.

9 is a graph showing cycle characteristic data when pre-potassinated carbon is used as an anode active material in a potassium ion secondary battery. In the case of a potassium secondary battery using as an anode active material, excellent life characteristics are exhibited without change in capacity even for several cycles at a reaction potential of 0V to 2V.

As described above, in the present invention, pre-potassinated carbon is used as a negative electrode material for a secondary battery, particularly a potassium ion secondary battery, and the initial irreversible capacity of the negative electrode material generated at the negative electrode during initial charge and discharge can greatly improve the initial efficiency.

In addition, pre-potassinated carbon can be used as an electrode conductive material of a secondary battery, particularly a potassium ion secondary battery. When a conventionally used conductive material (carbon black) is used as a conductive material for a potassium ion secondary battery, it shows low initial efficiency with a large initial irreversible capacity during initial charging and discharging. Instead, if pre-potassied carbon is used as a conductive material, the initial irreversible capacity can be greatly reduced and the initial efficiency can be greatly improved.

Accordingly, it is possible to secure initial efficiency, which is considered most important in a secondary battery, in particular, a potassium ion secondary battery electrode, and also improve capacity and cycle life. Furthermore, a secondary battery using the pre-potassinated carbon, particularly a potassium ion secondary battery, exhibits higher capacity, initial efficiency, and excellent cycle characteristics than typical carbon-based negative electrodes (graphite).

Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art can implement the present invention in other specific forms without changing its technical spirit or essential features. You will understand that there is Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

1: potassium ion secondary battery 11: negative electrode
12: anode 13: separator
14: battery container 15: sealing member
111: current collector 112: active material layer

Claims (9)

(a) preparing a mixed powder of potassium (K) and carbon (C); and
(b) applying mechanical energy to the mixed powder to cause a pre-potassiation reaction to produce pre-potassied carbon; . According to claim 1,
The carbon is characterized in that at least one selected from the group consisting of graphite-based carbon, carbon black-based carbon, activated carbon-based carbon, hard carbon, soft carbon, and carbon nanostructures. Method for producing prepotassiumized carbon. According to claim 1,
In step (b), a high-energy spex mill, a vibrotary-mill, a Z-mill, a planetary ball-mill or an attrition-mill A method for producing pre-potassiumized carbon, characterized in that by applying mechanical energy to the mill). According to claim 1,
Method for producing all-potassiumized carbon, characterized in that for producing all-potassiumized carbon represented by K _x C (X = 0.01 to 1) in the step (b). According to claim 1,
Method for producing pre-potassiumized carbon, characterized in that for producing a pre-potassiumized carbon powder having an average diameter of 1 nm or more and 500 μm or less in the step (b). An electrode conductive material for a potassium ion secondary battery comprising pre-potassiumized carbon prepared by the manufacturing method of any one of claims 1 to 5. An electrode active material for a potassium ion secondary battery comprising pre-potassiumized carbon prepared by the method of any one of claims 1 to 5. A secondary battery comprising the electrode conductive material for a potassium ion secondary battery according to claim 6. A secondary battery comprising the electrode active material for a potassium ion secondary battery according to claim 7 .

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