WO2018062619A1 - Sulfur dioxide-based redox flow secondary battery and electrolyte solution included therein - Google Patents

Abstract

The present invention relates to a sulfur dioxide-based redox flow secondary battery, the disclosed sulfur dioxide-based redox flow secondary battery comprising: a stack having an electrolyte solution injected therein; a cathode and an anode disposed in the stack; an electrolyte solution storage tank for storing the electrolyte solution and changing the electrolyte solution injected in the stack; and a pump used for injecting the electrolyte solution stored in the electrolyte solution storage tank into the stack, wherein the electrolyte solution comprises an inorganic liquid electrolyte comprising sulfur dioxide and a lithium salt or a sodium salt.

Description

Sulfur dioxide-based redox flow secondary battery and electrolyte contained therein

The present invention relates to a redox flow secondary battery, and more particularly to a sulfur dioxide-based redox flow secondary battery including a sulfur dioxide-based inorganic electrolyte.

There is a growing interest in greenhouse gas emissions in recent years. Accordingly, there is a need for a solution that can provide stable electric energy while reducing greenhouse gas emissions. As a solution to the above-described method, a large-capacity energy storage system in which renewable energy and a smart grid are fused has been proposed. Among the above-described large-capacity energy storage systems, the redox flow secondary battery is one of the most feasible technologies.

In the conventional redox flow secondary battery, a positive electrode and a negative electrode active material are dissolved in an electrolyte solution, the active material undergoes oxidation and reduction reactions on the surface of the positive electrode and the negative electrode, and ions are designed to move through the separator. Redox flow secondary batteries using the V / V redox couple and the Zn / Br redox couple are widely used, but have disadvantages of low cell voltage and low energy density. Thus, the development of redox couple using an organic solvent to implement a high voltage, but there is a flammability problem of the electrolyte by using an organic solvent.

In the existing redox flow secondary battery, the role of a separator capable of transferring ions and suppressing efficiency due to self-discharge is very important, and since anolyte and catholyte must be separated, a system employing two electrolyte reservoirs has been applied. Accordingly, the conventional redox flow secondary battery has a problem that it is difficult to reduce the volume as desired, and the design is complicated.

[Preceding technical literature]

[Patent Documents]

Korea Patent Registration No. 10-1335431 (2013.11.22.)

Accordingly, an object of the present invention is to provide a redox flow secondary battery capable of designing a battery using a sulfur dioxide inorganic liquid electrolyte capable of high voltage implementation and non-flammable lithium (or sodium) and a specified capacity and output form It is to provide an electrolyte solution included therein.

In addition, an object of the present invention and redox flow secondary battery comprising two electrolyte additives to improve the capacity reduction due to the limitation of the electrode surface due to the precipitation of NaCl, the discharge product of lithium (or sodium) sulfur dioxide secondary battery and It is to provide an electrolyte solution included.

Redox flow secondary battery of the present invention for achieving the above object is a stack in which the electrolyte is injected, a positive electrode and a negative electrode disposed in the stack, an electrolyte storage tank for storing the electrolyte and replacing the electrolyte injected into the stack, And a pump used to inject the electrolyte stored in the electrolyte reservoir into the stack, wherein the electrolyte comprises an inorganic liquid electrolyte composed of sulfur dioxide and lithium salt or sodium salt.

The electrolyte solution is characterized in that the molar ratio SO ₂ content NaAlCl ₄ compared to the 0.5 to 10.

The electrolyte is characterized in that the SO ₂ molar ratio content of NaAlCl ₄ is 1.5 ~ 3.0.

The electrolytic solution is characterized in that the nitro compound or aluminum chloride salt is added 0.1 to 5 times by weight ratio to the inorganic liquid electrolyte.

The electrolyte solution is characterized in that two or more salts are added to the inorganic liquid electrolyte.

The positive electrode is characterized in that the carbon material.

The negative electrode is made of at least one of lithium or sodium metal, an alloy containing lithium or sodium, an intermetallic compound containing lithium or sodium, and an inorganic material containing lithium or sodium.

Electrolyte solution included in the redox flow secondary battery of the present invention is characterized in that it comprises an inorganic liquid electrolyte, two or more salts added by 0.1 to 5 times by weight to the inorganic liquid electrolyte.

The two or more salts are characterized by comprising nitro compound and aluminum chloride salts.

As described above, according to the exemplary embodiment of the present invention, the redox flow secondary battery of the present invention may have a relatively simple configuration, have a nonflammability at a high voltage, and may provide a high power capacity.

1 is a view schematically showing a redox flow secondary battery configuration according to an embodiment of the present invention,

2 is a view showing an SEM image before and after the discharge of the surface of the lithium sulfur dioxide secondary battery positive electrode according to an embodiment of the present invention,

3 is a view showing the stability test results of the non-aqueous solvent according to an embodiment of the present invention,

4 is a view showing the degree of dissolution according to the electrolyte solution containing an additive according to an embodiment of the present invention,

5 is a view showing an example of a beaker cell for comparing redox flow secondary battery characteristics according to an embodiment of the present invention,

6 is a view showing discharge capacities for Comparative Example 1, Example 1, and Example 2 mentioned in Table 1 according to an embodiment of the present invention.

Prior to the description of the present invention, the terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, and the inventors should consider their own invention in the best way. For the purpose of explanation, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention on the basis of the principle that it can be properly defined as the concept of term. Therefore, the embodiments described in the present specification and the configuration shown in the drawings are only the most preferred embodiments of the present invention, and do not represent all of the technical ideas of the present invention, and various equivalents may be substituted for them at the time of the present application. It should be understood that there may be water and variations.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this case, it should be noted that like elements are denoted by like reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may blur the gist of the present invention will be omitted. For the same reason, some components in the accompanying drawings are exaggerated, omitted, or schematically illustrated, and the size of each component does not entirely reflect the actual size.

1 is a view schematically showing the configuration of a redox flow secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, the redox flow secondary battery 100 of the present invention may include a stack 110, an electrolyte reservoir 120, and a pump 130. In addition, the redox flow secondary battery 100 is a first connection connecting the electrolyte reservoir 120 and the stack 110, a second connection passage connecting the electrolyte reservoir 120 and the pump 130. In addition, the pump 130 may further include at least one of a third connection path connecting the stack 110. In addition, the redox flow secondary battery 100 may further include electrode portions respectively connected to the positive electrode and the negative electrode disposed in the stack 110. At least some of the electrode portions may be disposed to be exposed to the outside of the stack 110. The redox flow secondary battery 100 of the present invention described above uses a carbon material as a cathode and a cathode including lithium or sodium and a metal or an inorganic material including the same and without a separator. It is a hybrid type that can use a reservoir, and a structure including an inorganic electrolyte containing two kinds of additives can be adopted.

The stack 110 may be provided in various forms according to the shape of the product to be applied or the location of the product. According to one embodiment, the stack 110 may be provided in the form of a rectangular box. However, the present invention is not limited thereto, and the stack 110 may be variously modified according to the shape of the position to be disposed. The stack 110 may include a negative electrode 111, a positive electrode 112, and an electrolyte 113. In particular, the redox flow secondary battery 100 of the present invention may have a form in which no separator exists between the negative electrode 111 and the positive electrode 112.

The positive electrode 112 may be made of a porous carbon material. The positive electrode 112 has LiAlCl ₄ -xSO ₂ depending on the type of electrolyte filled in the stack 110. Or a place where the redox reaction of NaAlCl ₄ -xSO ₂ takes place. As one example, the positive electrode 112 may be fabricated using 10% PTFE binder in Ketjenblack 600JD. As another example, the cathode 112 may include 0 to 20 at% of one or more heteroatoms in the carbon material, and the heteroelements include nitrogen (N), oxygen (O), boron (B), and fluorine ( F), phosphorus (P), sulfur (S), and silicon (Si).

The negative electrode 111 may be provided using a lithium metal sheet. As another example, the negative electrode 111 may be formed of at least one of an alloy containing lithium, an intermetallic compound containing lithium, or an inorganic material containing lithium. The inorganic material may include at least one of carbon, oxides, sulfides, phosphides, nitrides, and fluorides.

The electrolyte 113 may include a sulfur dioxide-based metal compound. For example, Li (or Na) AlCl ₄ -xSO ₂ may be used as the electrolyte 113. The electrolyte 113 may be stored in the electrolyte reservoir 120 and supplied to the stack 110 by the pump 130.

The electrolyte reservoir 120 may be a reservoir for storing the electrolyte 113. The electrolyte storage tank 120 of the present invention may supply the stored electrolyte solution 113 to the stack 110 according to the operation of the pump 130.

The pump 130 may perform a pumping operation in response to the control of the controller. The amount of the electrolyte 113 supplied to the stack 110 varies according to the pumping operation of the pump 130. As a result, the amount of power generated by the reaction of the electrolyte 113 in the stack 110 varies. Accordingly, the pumping operation control of the pump 130 may vary depending on the amount of power supplied to the load. The pump 130 of the present invention may include one pump by using one electrolyte reservoir 120.

In addition, the redox flow secondary battery 100 of the present invention may be connected to a controller that performs the pumping speed control of the pump 130, and may also be connected to a load for supplying power generated from the redox flow secondary battery 100. have. In addition, heat may be generated in the process of moving the electrolyte 113 stored in the electrolyte storage tank 120 to the stack 110 to generate power, and this heat increases the temperature of the electrolyte storage tank 120. Accordingly, the redox flow secondary battery 100 may further include a cooling system for generating heat generated in the process of power generation and provision. The cooling system detects the temperature of the electrolyte reservoir 120 and cools the electrolyte reservoir 120 to have a predefined temperature. To this end, the cooling system may include a sensor for detecting the temperature of the electrolyte reservoir 120, and may perform cooling control of the electrolyte reservoir 120 based on the sensor signal collected by the sensor.

As described above, the redox flow secondary battery 100 of the present invention applies a sulfur dioxide-based lithium-based inorganic liquid electrolyte as an ion conductor and an active material, and a redox flow secondary battery to which one electrolyte storage tank 120 without a separator is applied. to be. Such a redox flow secondary battery 100 is simpler than a conventional redox flow secondary battery and can freely design a capacity and output of a sulfur dioxide-based lithium secondary battery, thereby providing a high voltage and nonflammable redox flow secondary battery. Can be. As described above, the lithium (or sodium) sulfur dioxide redox flow secondary battery has a merit that high voltage can be realized and safety can be secured by using a nonflammable liquid electrolyte.

In addition, the redox flow secondary battery 100 of the present invention may solve the capacity limitation problem due to the discharge product by removing the discharge product using two electrolyte additives.

FIG. 2 is a view showing SEM images before and after discharging the surface of a lithium sulfur secondary battery positive electrode; FIG. As shown, LiCl crystals are not formed on the surface of the positive electrode before the discharge 201, it can be clearly observed that the LiCl crystals formed on the surface of the positive electrode after the discharge (203).

Therefore, in order to improve driving and performance of the redox flow secondary battery by dissolving or dissolving LiCl (or NaCl), which is a discharge product generated after discharge, in the electrolyte storage tank 120, an additive for removing the discharge product in addition to the electrolyte solution 113. Or it may further comprise a solvent.

3 is a view showing the stability test results of the non-aqueous solvent according to an embodiment of the present invention.

Referring to FIG. 3, Pyridine-based 301, nitro compound 303, alcohol-based 305, and the like may be used as non-aqueous solvents capable of dissolving LiCl. However, one of the nitro compounds in the initial electrolyte and stability test may be used. Only nitrobenzene 303 has shown stable results with the electrolyte solution. However, when using a single solvent, such as nitro compound, there exists a problem which shows the limit of the dissolution of LiCl (or NaCl) which is a discharge product. Accordingly, the redox flow secondary battery 100 of the present invention uses a co-additive electrolyte additive capable of dissolving LiCl (or NaCl) in a large amount. For example, in the present invention, LiCl (or NaCl) solubility evaluation was performed by adding a new salt to the nitro compound of the SO ₂ electrolyte.

4 is a view showing the degree of dissolution according to the electrolyte solution containing an additive according to an embodiment of the present invention.

Will showing a state of FIG. 401 is a 4-nitro compound and the aluminum chloride salt at the same time dissolved SO ₂ in the electrolyte solution state, state 403 is a state dissolved 0.5M LiCl 2 jong salt (nitro-compounds and chlorinated aluminum salt) in the electrolyte SO ₂ It is shown. When using as the additive a salt (nitro-compounds and aluminum chloride) in the two above the SO ₂ electrolyte in SO ₂ may be co-dissolved in a nitro compound and the aluminum chloride salt in the electrolytic solution, a certain molar ratio as illustrated redox flow secondary Discharge products generated on the surface of the positive electrode during discharging of the battery may be dissolved to refresh the surface of the electrode. Nitro compound or aluminum chloride salt may be added to the SO ₂ electrolyte in an inorganic liquid electrolyte by 0.1 to 5 times by weight.

5 is a view showing an example of a beaker cell for comparing the characteristics of the redox flow secondary battery according to an embodiment of the present invention.

In order to compare the characteristics of the lithium dioxide redox flow secondary battery of the present invention described above, as shown in FIG. 5, there is no separator and there is no flow of electrolyte, but a beaker cell having a condition similar to a redox flow secondary battery is manufactured. Battery characteristics were compared. The beaker cell may include a beaker 501, an electrolyte 113, a negative electrode 111, a positive electrode 112, and a load. As described above, the electrolyte 113 may be either LiAlCl ₄ -xSO ₂ or NaAlCl ₄ -xSO ₂ . The positive electrode 112 may be made of a carbon material, and the negative electrode 111 may be a lithium-based metal sheet. The sulfur dioxide-based inorganic liquid electrolyte used as an electrolyte and a positive electrode active material is composed of LiAlCl ₄ (solute) and SO ₂ (solvent), and the content molar ratio of SO ₂ to LiAlCl ₄ corresponds to 0.5 to 10, preferably 1.5. Corresponds to ~ 3.

The battery configuration and electrode / electrolyte conditions of Examples and Comparative Examples are shown in Table 1 below.

		chief ingredient	Remarks
Comparative Example 1	Cathode	Ketjenblack 600JD		PTFE Binder 10% Electrode Area: 1.13㎠
	Anode	Li metal sheet	Electrode Area: 1.13㎠
	Electrolyte	LiAlCl 4 -xSO 2 3ml
Example 1	Cathode	Ketjenblack 600JD		PTFE Binder 10% Electrode Area: 1.13㎠
	Anode	Li metal sheet	Electrode Area: 1.13㎠
	Electrolyte	LiAlCl 4 -xSO 2 3ml + Nitrobenzene 3ml
Example 2	Cathode	Ketjenblack 600JD		PTFE Binder 10% Electrode Area: 1.13㎠
	Anode	Li metal sheet	Electrode Area: 1.13㎠
	Electrolyte	LiAlCl 4 -xSO 2 3ml + 3ml Nitrobenzene + AlCl 3

6 is a view showing discharge capacities for Comparative Example 1, Example 1, and Example 2 mentioned in Table 1 according to an embodiment of the present invention.

In the comparative example results in the embodiment as shown in Fig. 6, compare the same discharge capacity per active material LiAlCl ₄ -xSO ₂ Although the electrolyte was used, the electrolyte with Nitrobenzene additive was confirmed to result in an increase of about two times the discharge capacity. In addition, the electrolytic solution to which the co-additives of Nitrobenzene and aluminum chloride were applied was found to have a capacity increase of about 7 times that of the discharge capacity per area. This is because, as mentioned above, a large amount of the surface of the positive electrode electrode capable of electrode reaction can be obtained by dissolving a large amount of LiCl crystal as a discharge product.

While the present invention has been described using some preferred embodiments, these embodiments are illustrative and not restrictive. As such, those of ordinary skill in the art will appreciate that various changes and modifications can be made according to equivalents without departing from the spirit of the present invention and the scope of rights set forth in the appended claims.

[Description of the code]

100: redox flow secondary battery

110: stack

120: electrolyte storage tank

130: pump

Claims (8)

1. A stack into which electrolyte is injected;

   A positive electrode and a negative electrode disposed in the stack;

   An electrolyte reservoir for storing an electrolyte and replacing the electrolyte injected into the stack;

   And a pump used to inject the electrolyte stored in the electrolyte reservoir into the stack.

   The electrolyte solution

   A sulfur dioxide-based redox flow secondary battery comprising an inorganic liquid electrolyte composed of sulfur dioxide and lithium or sodium salts.
2. The method of claim 1,

   The electrolyte solution

   Sulfur dioxide-based redox flow secondary battery, characterized in that the molar ratio of SO ₂ to NaAlCl ₄ is 0.5 to 10.
3. The method of claim 2,

   The electrolyte solution

   Sulfur dioxide-based redox flow secondary battery, characterized in that the molar ratio of SO ₂ to NaAlCl ₄ is 1.5 ~ 3.0.
4. The method of claim 1,

   The electrolyte solution

   A sulfur dioxide-based redox flow secondary battery comprising 0.1 to 5 times the weight ratio of nitro compound or aluminum chloride salt to an inorganic liquid electrolyte.
5. The method of claim 1,

   The electrolyte solution

   A sulfur dioxide-based redox flow secondary battery comprising two or more salts added to an inorganic liquid electrolyte.
6. The method of claim 1,

   The positive electrode is made of a carbon material,

   The negative electrode is a sulfur dioxide-based redox flow secondary battery, characterized in that made of at least one of lithium or sodium metal, an alloy containing lithium or sodium, an intermetallic compound containing lithium or sodium, and an inorganic material containing lithium or sodium.
7. In the electrolyte used for the redox flow secondary battery,

   Inorganic liquid electrolytes;

   Two or more salts added in an amount of 0.1 to 5 times by weight to the inorganic liquid electrolyte;

   Electrolyte used in the sulfur dioxide-based redox flow secondary battery comprising a.
8. The method of claim 7, wherein

   The two or more salts are

   An electrolytic solution for a sulfur dioxide-based redox flow secondary battery comprising nitro compound and aluminum chloride salt.

Images