KR102287470B1 - Porphyrin based catalyst system, cathode of lithium battery using the porphyrin based catalyst system, and lithium battery including the cathode of lithium battery - Google Patents

Abstract

Disclosed are a porphyrin-based catalyst system, a cathode for a lithium battery using the catalyst system, and a lithium battery including the cathode for a lithium battery. The porphyrin-based catalyst system according to an embodiment may include a porphyrin-based catalyst in which a central metal of the porphyrin is substituted with a transition metal.

Description

A porphyrin-based catalyst system, a positive electrode for a lithium battery using the catalyst system, and a lithium battery including the positive electrode for a lithium battery }

The following description relates to a porphyrin-based catalyst system, a lithium battery positive electrode using the catalyst system, and a lithium battery including the lithium battery positive electrode.

With the development of industrial technology, the consumption of fossil fuels has rapidly increased, and the supply of electric vehicles and hybrid vehicles is also expanding in order to reduce carbon dioxide emissions. Current lithium-ion batteries do not allow long-distance driving of electric vehicles due to limitations in battery capacity, and when multiple batteries are packed and used to cover the capacity, not only increase the weight of the vehicle but also sales. Because it causes an increase in price, it is not suitable for commercial use of electric vehicles. For long-distance operation equivalent to the gasoline-based vehicle of an electric vehicle, a large-capacity battery must be installed in the electric vehicle, and a secondary battery having an energy density five times greater than that of a conventional battery is required.

Accordingly, a lithium-air battery having a greater energy density than that of a lithium ion battery is attracting attention. Unlike lithium ion batteries, lithium-air batteries use oxygen in the atmosphere as an active material (active material: a material that chemically reacts to produce electrical energy when the battery is discharged), unlike lithium-ion batteries, so there is an advantage in terms of supply and demand of raw materials.

These lithium-air batteries mainly use a positive electrode composed of porous carbon for smooth oxygen movement, and during discharge, lithium ions move from the negative electrode to the air electrode and oxygen reduction reaction (2Li ⁺ + O ₂ +2e ^- → Li ₂ O ₂ , Oxygen reduction reaction, ORR) produces electricity, and the standard voltage at this time is thermodynamically reacted at 2.96V according to the Nernst formula. Conversely, if a voltage higher than the standard voltage is applied from the outside, the reverse reaction of oxygen evolution (Li ₂ O ₂ → 2Li ⁺ + O ₂ +2e ^- , Oxygen Evolution Reaction, OER) takes place at the cathode and charging is performed.

However, in lithium-air batteries, solid lithium oxide (Li ₂ O ₂ ), a reaction product, is not reversibly decomposed but accumulates on the electrode surface to block micropores, thereby reducing the specific reaction surface area or preventing the inflow of electrolyte and oxygen. It has a fundamental problem, such as clogging, the voltage required for charging and discharging of the electrode is increased (Overpotential). In other words, an overvoltage much higher than the standard voltage must be applied to charge the lithium-air battery, which in turn results in energy loss.

Various electrochemical catalysts have been studied so far, noble metal catalysts such as Au, Ag, Pt, Pd, Ru or Ir, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , Co ₃ O ₄ , CuO, Fe ₂ Transition metal oxide-based catalysts such as O ₃ , NiO, CeO ₂ , LaMnO ₃ , MnCo ₂ O ₄ or Ba _0.5 Sr _0.5 Co _0.2 Fe _0.8 O ₃ are combined with carbon materials and introduced into the cathode to improve battery efficiency has been going on a lot. However, the problem of deactivation of the catalyst surface due to the lithium oxide or lithium carbonate-based surface product and the price increase of the transition metal oxide occurred.

Therefore, there is a need to develop a high-efficiency catalyst applicable to a lithium oxygen battery and/or a lithium air battery.

Prior art literature

(Patent Document 0001) Republic of Korea Patent Publication No. 10-2017-0089122

A porphyrin-based catalyst system for a lithium battery is provided.

A positive electrode for a lithium battery to which the catalyst system is applied is provided.

It provides a lithium battery including the positive electrode for the lithium battery.

It provides a catalyst system comprising a porphyrin-based catalyst in which the central metal of porphyrin is substituted with a transition metal.

According to one side, the transition metal is titanium (Ti), copper (Cu), iron (Fe), zinc (Zn), vanadium (V), manganese (Mn), nickel (Ni-Porphyrin) and cobalt (Co) It may be characterized in that it comprises at least one metal.

According to another aspect, the porphyrin-based catalyst may be characterized in that it is included in an electrolyte that transfers lithium ions generated in the negative electrode for a lithium battery to the positive electrode for a lithium battery.

According to another aspect, as the ion of the central metal located in the center of the porphyrin binds and desorbs oxygen as the active material of the positive electrode for a lithium battery, the oxidation number of the ion of the central metal changes, and the electron transfer reaction for the positive electrode for the lithium battery (electron transfer reaction) can be characterized by deriving.

According to another aspect, the degree of promoting the charge reaction (Oxygen Evolution Reaction, OER) and the discharge reaction (Oxygen Reduction Reaction, ORR) according to the redox potential of the metal ion according to the type of the substituted metal as the central metal of the porphyrin may be characterized as being different.

According to another aspect, it may be characterized in that the ion of the substituted metal as the central metal of the porphyrin binds and desorbs with oxygen as the active material of the positive electrode for a lithium battery in an oxygen atmosphere.

According to another aspect, it may be characterized in that the ion of the metal substituted as the central metal of the porphyrin binds and desorbs with oxygen as the active material of the positive electrode for a lithium battery in an air atmosphere.

The performance of a lithium battery may be improved by utilizing porphyrin as a catalyst included in the electrolyte.

Without a complicated electrode manufacturing process, cell performance can be improved only by including porphyrin in the electrolyte of an existing lithium battery, which enables mass production of electrodes, thereby reducing production costs.

1 is a view showing the operating principle of a porphyrin-based redox mediator (Redox Mediator, RM) as a catalyst for a lithium battery according to an embodiment of the present invention.
2 and 3 are graphs illustrating examples of cyclic voltammetry (CV) measurement results in an oxygen purge cell using a porphyrin catalyst including various metal ions, according to an embodiment of the present invention.
4 and 5 are graphs showing examples of charge/discharge curves in an oxygen purge cell using a porphyrin catalyst including various metal ions in an embodiment of the present invention.
6 and 7 are graphs showing examples of CV measurement results in an air purge cell using a porphyrin catalyst including various metal ions in an embodiment of the present invention.
8 and 9 are graphs showing examples of charge/discharge curves in an air purge cell using a porphyrin catalyst including various metal ions in an embodiment of the present invention.
10 is a graph showing an example of CV measurement results in an oxygen purge cell when nickel and vanadium are mixed according to an embodiment of the present invention.
11 is a graph showing an example of CV measurement results in an oxygen purge cell when zinc and manganese are mixed according to an embodiment of the present invention.
12 is a graph illustrating an example of CV measurement results in an air purge cell when nickel and vanadium are mixed according to an embodiment of the present invention.
13 is a graph showing an example of CV measurement results in an air purge cell when zinc and manganese are mixed according to an embodiment of the present invention.
14 is a graph illustrating an example of a charge/discharge curve in an oxygen purge cell when zinc and manganese are mixed according to an embodiment of the present invention.
15 is a graph illustrating an example of a charge/discharge curve in an air purge cell when zinc and manganese are mixed according to an embodiment of the present invention.

The present invention can apply various transformations and can have various embodiments. Hereinafter, specific embodiments will be described in detail based on the accompanying drawings.

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

1 is a view showing the operating principle of a porphyrin-based redox mediator (Redox Mediator, RM) as a catalyst for a lithium battery according to an embodiment of the present invention.

Porphyrin is a rich raw material commonly found in natural chlorophyll or blood. When porphyrin is used as a raw material for a catalyst for lithium batteries, it has a very large price competitiveness. For example, hemoglobin (Hb) is a respiratory molecule found in the red blood cells of vertebrates, and functions to transport oxygen from the lungs to the body cells and carbon dioxide from the body cells to the lungs. One hemoglobin molecule consists of four polypeptide chains, and each polypeptide chain contains one heme group consisting of a tetrapyridyl ring chelated to an ^{Fe 2+ ion.} In the lungs, the iron atom of the hemoglobin molecule reversibly binds to a molecule of oxygen, which is then transported to the body cells as the blood circulates. Then, the oxygen is released from the hemoglobin molecules in the tissue, and then the oxygen-free hemoglobin molecules absorb carbon dioxide, which returns to the lungs and then is released from the lungs. That is, hemoglobin serves to transport oxygen or carbon dioxide in a living body. Chlorophyll also binds and desorbs oxygen.

In other words, unlike the existing redox mediators that only transfer charges, the porphyrin-based electrolyte catalyst has a complex function of actively repeating binding and desorption with oxygen molecules. As an example, Scheme 1 below shows an electron transfer reaction by a conventional redox mediator, and Scheme 2 below shows an electron transfer reaction by a porphyrin-based redox mediator that repeats active binding and desorption with oxygen molecules. An electron transfer reaction is shown.

[Scheme 1]

RM ⁺ + e ^- → RM

[Scheme 2]

RM(M ³⁺ ) + O ₂ + e ^- → RM(M ²⁺ ) - O ₂

Here, "M" in Scheme 2 may mean a metal ion located at the center of the porphyrin structure. As these metal ions combine with oxygen, the oxidation number changes (M ²⁺ ↔ M ³⁺ + e ^- ), and the electrochemical redox driving voltage (Redox potential) may change depending on the type of metal ion. In other words, since the degree of promoting the charging reaction (Oxygen Evolution Reaction, OER) and the discharging reaction (Oxygen Reduction Reaction, ORR) varies depending on the redox potential of the central metal ion in the porphyrin, the optimal central metal ion is introduced. it is important to do

In addition, the porphyrin-based redox mediator according to this embodiment can tune the reaction voltage of the soluble catalyst by substituting the central metal (M), and various functional groups (eg, CO ₂ H, SCH ₃ , NO _{2 )} , OH, NH ₂ , SH), it is possible to tune the type of substance group that reacts to the soluble catalyst.

As such, in the embodiment of the present invention, by introducing porphyrin as an electrolyte catalyst, the performance of a lithium battery such as a lithium oxygen battery or a lithium-air battery in an atmospheric atmosphere can be improved, and the redox characteristics of the electrolyte catalyst by substituting a central metal ion and Catalyst activity can be adjusted during charging and discharging.

In addition, by distinguishing the porphyrin catalyst for charge reaction activity and the porphyrin catalyst for discharge reaction activity, and by appropriately mixing two different porphyrin catalysts, a porphyrin catalyst having bifunctionality during charge and discharge can be provided.

2 and 3 are graphs illustrating examples of cyclic voltammetry (CV) measurement results in an oxygen purge cell using a porphyrin catalyst including various metal ions, according to an embodiment of the present invention. The graphs of FIGS. 2 and 3 show the case of using an electrolyte in which lithium bismide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) are mixed, and using various electrolyte catalysts under the condition ^{that the scan rate is 5 mVs −1} CV measurement results in an oxygen purge cell (O ₂ Purged Cell) are shown. Here, as various electrolyte catalysts, as shown in FIGS. 2 and 3, a cell (Pristine) that does not introduce a porphyrin catalyst, a porphyrin (Ti-Porphyrin) in which a titanium ion is substituted with a central metal ion, and a copper ion is substituted with a central metal ion One porphyrin (Cu-Porphyrin), a porphyrin in which an iron ion is substituted with a central metal ion (Fe-Porphyrin), a porphyrin in which a zinc ion is substituted for a central metal ion (Zn-Porphyrin), and a porphyrin in which a vanadium ion is substituted for a central metal ion (V-Porphyrin), porphyrin with a manganese ion replaced with a central metal ion (Mn-Porphyrin), porphyrin with a nickel ion replaced with a central metal ion (Ni-Porphyrin), and porphyrin with a cobalt ion replaced with a central metal ion (Co) -Porphyrin) and Cu-centered chlorophyllin were utilized, respectively. According to these measurement results, in the oxygen evolution reaction (OER), the catalytic activity of the oxygen evolution reaction was high in the order of Zn-Porphyrin, Ni-Porphyrin, V-Porphyrin, Cu-Porphyrin, Fe-Porphyrin, and Co-Porphyrin. In the oxygen reduction reaction (ORR), the oxygen reduction reaction is in the order of Mn-Porphyrin, Fe-Porphyrin, Zn-Porphyrin, V-Porphyrin, Ni-Porphyrin, Cu-Porphyrin, Co-Porphyrin, and Ti-Porphyrin. The catalytic activity was high.

In other words, the graphs of FIGS. 2 and 3 show that the catalytic activity in the oxygen purge cell of the porphyrins substituted with specific metal ions is higher than that of the cell (Pristine) or Cu-centered Chlorophyllin without the introduction of the porphyrin catalyst. indicates relatively high. In addition, it can be seen that the porphyrin catalyst suitable for the charge reaction activity in the oxygen purge cell and the porphyrin catalyst suitable for the discharge reaction activity are different.

4 and 5 are graphs showing examples of charge/discharge curves in an oxygen purge cell using a porphyrin catalyst including various metal ions in an embodiment of the present invention. The graphs of FIGS. 4 and 5 show that all porphyrins except Cu-centered chlorophyllin have a lower overvoltage than that of the cell (Pristine) without introducing the porphyrin catalyst in the charging region (OER region) (Mn- Porphyrin > Zn-Porphyrin > Co-Porphyrin > Fe-Porphyrin = V-Porphyrin > Ni-Porphyrin = Ti-Porphyrin > Cu-Porphyrin). In the case of Mn-porphyrin, the reaction start voltage of the discharge is about 2.87 V, which is higher than 2.5 V in the cell (pristine) without the introduction of the porphyrin catalyst, indicating that it is excellent in the discharge region (ORR region). In the case of co-porphyrin and Zn-porphyrin, the discharge overpotential is greater than that of the cell without the porphyrin catalyst (Pristine) in the ORR region, and the other porphyrins have a significant difference from the cell without the porphyrin catalyst (Pristine). there was no

6 and 7 are graphs showing examples of CV measurement results in an air purge cell using a porphyrin catalyst including various metal ions in an embodiment of the present invention. The graphs of FIGS. 6 and 7 show the case of using an electrolyte in which lithium bismide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) are mixed, and using various electrolyte catalysts under the condition ^{that the scan rate is 5 mVs −1 .} CV measurement results in an air purged cell of According to these measurement results, in the oxygen evolution reaction (OER), unlike in the oxygen purge cell described with reference to FIGS. 2 and 3 , Mn-Porphyrin, Ni-Porphyrin, Co-Porphyrin, Cu-Porphyrin, Fe- In the order of Porphyrin, V-Porphyrin, and Zn-Porphyrin, the catalytic activity of oxygen evolution reaction was high. Also, in the oxygen reduction reaction (ORR), unlike in the oxygen purge cell described with reference to FIGS. 2 and 3 , Mn-Porphyrin, Ti-Porphyrin, Fe-Porphyrin, Co-Porphyrin, Zn-Porphyrin, Ni- In the order of Porphyrin and Cu-Porphyrin, the oxygen reduction reaction catalytic activity was high.

Nevertheless, the graphs of FIGS. 6 and 7 show the catalytic activity in the air purge cell of the porphyrins substituted with specific metal ions rather than the cells (Pristine) or Cu-centered chlorophyllin without the introduction of the porphyrin catalyst. This indicates that it is relatively high. In addition, in the air purge cell, it can be seen that the porphyrin catalyst suitable for the charge reaction activity and the porphyrin catalyst suitable for the discharge reaction activity are different.

8 and 9 are graphs showing examples of charge/discharge curves in an air purge cell using a porphyrin catalyst including various metal ions in an embodiment of the present invention. In the graphs of FIGS. 8 and 9, all types of porphyrins have a lower overvoltage than the cell (Pristine) without introducing the porphyrin catalyst in the charging region (OER region) (Mn-Porphyrin > Co-Porphyrin, Ni-Porphyrin, Fe-Porphyrin > Zn-Porphyrin, Ti-Porphyrin, V-Porphyrin > Cu-Porphyrin > Cu-centered chloropyllin). In addition, in the discharge region (ORR region), most of the porphyrins are similar to the cell (Pristine) to which the porphyrin catalyst is not introduced.

On the other hand, as already described, it can be seen that the porphyrin catalyst suitable for the charge reaction activity and the porphyrin catalyst suitable for the discharge reaction activity are different in both the oxygen purge cell and the air purge cell. Hereinafter, the porphyrin catalyst for charge reaction activity and the porphyrin catalyst for discharge reaction activity are distinguished, and two different porphyrin catalysts are appropriately mixed to describe a porphyrin catalyst having bifunctionality during charge and discharge.

10 is a graph showing an example of CV measurement results in an oxygen purge cell when nickel and vanadium are mixed according to an embodiment of the present invention. In the embodiment of FIG. 10, a porphyrin catalyst using nickel (Ni) ions as a central metal ion and a porphyrin catalyst using vanadium (V) as a central metal ion are mixed (Ni + V blending) and added to the electrolyte in the oxygen purge cell. CV measurement results are shown. At this time, the graph of FIG. 10 shows the catalytic effect in the OER region and the ORR region when compared to the cell (Pristine) without the introduction of the porphyrin catalyst in the case of Ni + V blending, but Ni-porphyrin and V-porphyrin each material separately When compared, it shows that the effect is reduced.

11 is a graph showing an example of CV measurement results in an oxygen purge cell when zinc and manganese are mixed according to an embodiment of the present invention. In the embodiment of FIG. 11, a porphyrin catalyst using zinc (Zn) ions as a central metal ion and a porphyrin catalyst using manganese (Mn) as a central metal ion are mixed (Zn + Mn blending) in an oxygen purge cell added to the electrolyte. CV measurement results are shown. At this time, in the graph of FIG. 11 , Zn + Mn blending also shows a similar shape to that in the case of using only Mn-porphyrin rather than simultaneously having a catalytic effect when using each of Zn-porphyrin and Mn-porphyrin as a catalyst.

12 is a graph illustrating an example of CV measurement results in an air purge cell when nickel and vanadium are mixed according to an embodiment of the present invention. In the embodiment of FIG. 12, a porphyrin catalyst using nickel (Ni) ions as a central metal ion and a porphyrin catalyst using vanadium (V) as a central metal ion are mixed (Ni + V blending) in an air purge cell added to the electrolyte. CV measurement results are shown. At this time, the graph of FIG. 12 shows that when Ni + V blending is compared with each of Ni-porphyrin and V-porphyrin individually, the effect is reduced.

13 is a graph illustrating an example of CV measurement results in an air purge cell when zinc and manganese are mixed according to an embodiment of the present invention. In the embodiment of FIG. 13, a porphyrin catalyst using zinc (Zn) ions as a central metal ion and a porphyrin catalyst using manganese (Mn) as a central metal ion are mixed (Zn + Mn blending) in an air purge cell added to the electrolyte. CV measurement results are shown. At this time, the graph of FIG. 13 shows that in the case of Zn + Mn blending, the catalytic effect of air Zn-porphyrin and Mn-porphyrin is simultaneously shown, and the catalytic effect is shown in both the ORR region and the OER region.

14 is a graph illustrating an example of a charge/discharge curve in an oxygen purge cell when zinc and manganese are mixed according to an embodiment of the present invention. In the embodiment of FIG. 14, a porphyrin catalyst using zinc (Zn) ions as a central metal ion and a porphyrin catalyst using manganese (Mn) as a central metal ion are mixed (Zn + Mn blending) in the air purge cell added to the electrolyte. A charge-discharge curve is shown. At this time, in the graph of FIG. 14, in the case of Zn + Mn blending, compared to the cell (Pristine) without introducing the porphyrin catalyst in an oxygen atmosphere, the performance is good, but when compared with the respective materials of Zn-porphyrin and Mn-porphyrin, the effect is not Rather, it shows a decrease.

15 is a graph illustrating an example of a charge/discharge curve in an air purge cell when zinc and manganese are mixed according to an embodiment of the present invention. In the embodiment of FIG. 15, a porphyrin catalyst using zinc (Zn) ions as a central metal ion and a porphyrin catalyst using manganese (Mn) as a central metal ion are mixed (Zn + Mn blending) in the air purge cell added to the electrolyte. A charge-discharge curve is shown. At this time, the graph of FIG. 15 shows a lower overvoltage and a higher discharge reaction start voltage (about 2.9 V) than when Zn-porphyrin and Mn-porphyrin exist separately in the case of Zn + Mn blending when mixed in an atmospheric atmosphere. As shown, the catalytic effect was verified in the actual charge/discharge experiment as in the CV measurement result of FIG. 15 .

Meanwhile, in the above description, titanium (Ti), copper (Cu), iron (Fe), zinc (Zn), vanadium (V), manganese (Mn), nickel (Ni-Porphyrin) and cobalt as the central metal ion of the porphyrin catalyst Although the ion of at least one metal among (Co) is described, the metal ion that can be substituted in the center of the porphyrin catalyst can be extended to the ion of the transition metal.

The above description is merely illustrative of the technical spirit of the present invention, and various modifications and variations will be possible without departing from the essential characteristics of the present invention by those skilled in the art to which the present invention pertains. Accordingly, the embodiments described in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and are not limited to these embodiments. The protection scope of the present invention should be construed by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims (7)

It contains a porphyrin-based catalyst in which the central metal of porphyrin is substituted with a transition metal,
The metal substituted as the central metal of the porphyrin binds and desorbs with oxygen as an active material of the positive electrode for a lithium battery in an air atmosphere,
The porphyrin-based catalyst uses titanium (Ti), copper (Cu), iron (Fe), zinc (Zn), vanadium (V), manganese (Mn), nickel (Ni-Porphyrin) and cobalt (Co) as the central metal of porphyrin. ) a first porphyrin-based catalyst substituted with a first metal selected from the group containing including,
The catalytic effects of the first porphyrin-based catalyst and the second porphyrin-based catalyst vary depending on the type of metal selected as the first metal and the second metal
Catalyst system characterized in that. delete According to claim 1,
The porphyrin-based catalyst is a catalyst system, characterized in that it is included in the electrolyte for transferring lithium ions generated in the negative electrode for a lithium battery to the positive electrode for a lithium battery. According to claim 1,
As the ion of the central metal located in the center of the porphyrin binds to and desorbs oxygen as the active material of the positive electrode for a lithium battery, the oxidation number of the ion of the central metal changes, and an electron transfer reaction for the positive electrode for the lithium battery is performed. Catalyst system, characterized in that for deriving. According to claim 1,
The degree of promoting the charge reaction (Oxygen Evolution Reaction, OER) and the discharge reaction (ORR) is different according to the redox potential of the metal ion according to the type of metal substituted as the central metal of the porphyrin. catalyst system. According to claim 1,
Catalyst system, characterized in that the ion of the substituted metal as the central metal of the porphyrin binds and desorbs with oxygen as the active material of the positive electrode for a lithium battery in an oxygen atmosphere. According to claim 1,
Catalyst system, characterized in that the ion of the substituted metal as the central metal of the porphyrin binds and desorbs with oxygen as the active material of the positive electrode for a lithium battery in an air atmosphere.

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