KR20160059974A - Battery system and redox flow battery comprising same - Google Patents

Abstract

The present invention relates to a battery system, and a redox flow battery including the battery system. The battery system comprises: a positive electrolyte (catholyte) including an acid electrolyte; a negative electrolyte (anolyte) including a basic electrolyte; and a solid electrolyte separation membrane for moving only positive ion, wherein the negative electrolyte and the positive electrolyte are introduced in a double flow manner. The battery system of the present invention can be implemented in a high voltage, can be installed with low costs, can store a large capacity, can be operated in a room temperature, and can be used for a long time, unlike the conventional battery system. In addition, new types of positive and negative active material couples are applied to the battery system, instead of positive and negative active material couples used for a single electrolyte, and the battery system is composed of a water-based system, compared to a non-aqueous Li-ion second battery, whereby there is no risk of explosion and pollution of environment, and 85% or more of inversion efficiency can be implemented.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery system and a redox flow battery including the battery system.

[0001] The present invention relates to a novel battery system and a redox flow cell comprising the same, and more particularly, to a battery system comprising a negative electrode electrolyte containing an acidic electrolyte and a positive electrode electrolyte, A battery system in which an electrolyte is introduced by a double flow method, and a redox flow cell including the same.

The Energy Storage System (ESS) is a system that stores the generated energy in a grid and supplies it to the most necessary time to improve energy efficiency. The advantage of an energy storage system is that it contributes to the optimization of power operation through load leveling and stores idle power at light load and can be used in overloading. In addition, since the renewable energy source can be converted to high-quality power and linked to the power network, it can be applied to an energy source having a severe output fluctuation such as sunlight and wind power.

The energy storage system is composed of lithium-ion (Li-Ion), super capacitor, flywheel, flow battery in the field of short time, NaS and CAES It can be classified according to the energy output and the usage time. The short-term energy storage system used for short seconds or minutes is mainly aimed at improving the power quality, and lithium-ion batteries, supercapacitors, and flywheels are available. Long-term energy storage systems used for long time are mainly used for power load leveling, and they include compressed air, NaS cells, and redox flow batteries (RFBs).

Lead-acid batteries, which are most widely used in energy storage systems, are advantageous in that they are inexpensive and stable, but are non-environmentally lead-containing and have a short life span. Lithium-ion batteries account for 50% of the small-sized battery market, but it is difficult to increase the capacity of the small-sized battery market and the possibility of explosion of high-temperature batteries is limited. In addition, the NaS cell has a high energy density, but it has disadvantages such as emission of sulfur gas during driving and maintenance of high temperature and high production cost.

It is necessary to examine the stability, long life, and recycle of materials as storage conditions necessary for large energy storage. Among these, the redox flow cell is an energy storage system which can satisfy all of the above-mentioned selection conditions and is easy to be mass-produced and expected to be applied to a smart grid or a distributed power source. On the other hand, in the energy storage system industry centered on the United States, the compressed air CAES market was expected to lead the energy storage system market, but the battery was used to store compressed air in confidential underground storage such as salt animals, , The use of fossil fuels is inevitable. Recently, it seems that other technologies than CAES will occupy a large part of the energy storage system market.

In particular, the redox flow battery is expected to occupy a large market in the future. Unlike other secondary batteries using solid active materials, the redox flow battery has a very long charge / discharge cycle life because it does not desorb the active material, and the electrolyte can be used semi-permanently. In addition, the output (kW) in the stack portion and the capacity (kWh) in the electrolyte tank portion can be individually controlled, so that a customized design can be made according to the use. Other secondary batteries such as lithium ion batteries require periodic compensation operations to prevent varying the charge amount for each cell, but the redox flow cells are provided with an electrolyte solution in the same tank and the charge states of each stack remain substantially the same Even if the compensation operation is unnecessary and the battery is stopped for a long period of time, the electrolytic solution having electric energy is separated from the anode and the cathode tanks, and thus the electric loss is very small.

One of the most popular redox flow cells is the all vanadium redox flow battery such as Korean Patent Laid-Open No. 10-2015-0040753. The vanadium redox flow cell is driven by an expensive ion exchange membrane, such as Nafion, and a flux to the two electrolytes (cathode and anode). The redox flow cell has the advantages of low energy density, energy loss due to self-discharge, and non-economy due to cross-over of ions, solubility of active material, mixed contamination of electrolytes and irreversibility of redox couples. We are exposing the problem. In order to solve these problems, many researches and developments have been made, but the performance suitable for commercialization has not yet been realized.

The present invention relates to a battery system and a redox flow cell comprising the battery system.

An object of the present invention is to provide a method of manufacturing a semiconductor device, comprising: a first external reservoir including a positive electrode electrolyte comprising an acidic electrolyte; A second external reservoir including a negative electrode electrolyte including a basic electrolyte; electrode; A solid electrolyte separator for moving only cations; And a bipolar plate, wherein the acidic electrolyte comprises a cathode active material, wherein the basic electrolyte comprises a negative active material, and the anode and cathode electrolyte are injected into a cathode and an anode in a double injection manner, .

Another object of the present invention is to develop a new positive electrode and negative electrode active material couples that can be applied to the redox flow cell of the present invention rather than the positive and negative electrode active material couples used in a single electrolyte, System, which is free from the risk of explosion and environment, and can realize a reversal efficiency of 85% or more, and a redox flow cell including the battery system.

Still another object of the present invention is to provide a cathode electrolyte comprising a negative electrode active material; A positive electrode electrolyte (Anolyte) containing a positive electrode active material; electrode; And a solid electrolyte separator for transferring only the positive ions, wherein each of the electrolytes is injected into and recovered from an electrode, circulated, and the positive electrode active material and the negative electrode active material respectively undergo redox reaction, Battery system.

Other objects and advantages of the present invention will become more apparent from the following detailed description of the invention and claims.

Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art, and the following embodiments can be modified into various other shapes, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the invention to those skilled in the art.

In the drawings, the thickness and size of each layer are exaggerated for convenience and clarity of description, and the same reference numerals refer to the same elements in the drawings. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, a singular form may include a plurality of shapes, unless the context clearly dictates otherwise. Also, " comprise "and / or" comprising "when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

Unlike conventional secondary batteries, the redox flow battery in the present invention is a system in which an active material in an electrolyte is oxidized and reduced to be charged and discharged. The redox flow battery is an electrochemical storage device for storing chemical energy of an electrolyte directly as electric energy .

As shown in FIG. 1, when the battery system is separated according to the injection method, it is largely divided into a single injection and a double injection, and a single injection system is distinguished by the absence of a separation membrane and the use of an acid as an electrolyte and a basicity. In the case of double injection, a separation membrane is essentially used, and it is also possible to distinguish the case where the acid is used only as the electrolyte, the case where only the base is used, and the case where the acid / base is used in both cases. When a single acid or a base electrolyte is used, it is difficult to realize a high voltage. However, in the case of the redox flow battery and the battery system according to one embodiment of the present invention, since both the acid / , And a high-voltage battery can be realized.

Because the redox battery stores electricity in the electrolyte, it increases the stored power by increasing the electrolyte, not by increasing the cell. Since the cell and the electrolyte can be separated and installed, the stored electrolyte is stored in a closed container Power can be stored at low cost over a long period of time. Because redox batteries do not require special manufacturing facilities to make them, they can be manufactured in a small size (several watts) to large (tens of thousands of kilowatts).

Unlike conventional rechargeable batteries, the redox battery is an electrochemical storage device in which the active energy of the electrolyte is oxidized and reduced to charge and discharge, and the chemical energy of the electrolyte is stored directly as electrical energy.

In one embodiment of the present invention, the battery of the present invention comprises a first external reservoir containing a positive electrode electrolyte comprising an acidic electrolyte; A second external reservoir including a negative electrode electrolyte including a basic electrolyte; electrode; A solid electrolyte separator for moving only cations; And a bipolar plate, wherein the acidic electrolyte comprises a cathode active material, the basic electrolyte comprises a cathode active material, and the cathode and the anode electrolyte are injected into a cathode and an anode in a double injection manner .

More specifically, the redox flow cell comprises an external reservoir in which an electrolyte containing an active material is stored, an electrode in which an electrochemical reaction of the active material occurs, an anode and a cathode electrolyte, and an electrode for protecting the electrode from pressure applied during stacking A bipolar plate, a separator for preventing direct contact between the positive and negative electrode electrolytes, and for preventing permeation of cations and permeation of active ions. It consists of an external reservoir that stores the electrolyte, so that the output and capacity can be freely designed. Since the electrolyte is supplied from the external storage tank, the charging state of each battery cell is the same, so that operation such as cell balancing is unnecessary. Further, no exhaust gas such as CO ₂ is generated.

In one embodiment of the present invention, the battery of the present invention includes a solid electrolyte separator for moving only positive ions, and the solid electrolyte separator is a solid electrolyte separator capable of moving cations of Group 1 and Group 2 metals, Preferably at least one selected from the group consisting of Na +, Li + and K +, more preferably K +, but is not limited thereto.

The solid electrolyte separator generally has: 1) high selectivity of ions 2) low electrical resistance 3) low diffusion coefficient of solute and solvent 4) chemically stable 4) excellent mechanical strength 2) is a conceptual view of a solid electrolyte separator. According to FIG. 2, a typical solid electrolyte separator has a high selective permeability of 2H +, and a permeability of an ionic active material It must be able to prevent it. However, when the Nafion membrane is applied to a battery, there is a problem that energy efficiency is deteriorated due to permeation of the ionic active material. In order to prevent such problems, a method of bonding a conductive polymer such as polyaniline or polypyrroline to a microporous PVC membrane and an ultra-microporous filter membrane, CMV or AMV, or a silica- filled PE, PE symmetric membranes, and asymmetric membranes cross-linked with electron beams.

The solid electrolyte separator according to one embodiment of the present invention relates to a solid electrolyte separator which permits migration of cations of Group 1 and Group 2 metals while preventing permeation of an ionic active material, and is excellent in energy efficiency. Here, the cation is a cation of a Group 1 or Group 2 metal, and is preferably at least one selected from the group consisting of Na +, Li + and K +, more preferably K +, but is not limited thereto.

In one embodiment of the present invention, the solid electrolyte separator of the present invention has a void volume of 30 to 70%, a pore size of 0.05 to 0.1 탆, and a thickness of 0.3 to 1.0 mm. Due to the pore volume and pore size, unlike conventional separators, K + can be moved. That is, when the pore volume is less than 30% and the pore size is less than 0.05 mu m, K + migration is not possible. When the pore volume is more than 70% and the pore size is more than 0.1 mu m, There is a problem of low energy efficiency. If the thickness is less than 0.3 mm, the selective permeation speed of the ions is increased to increase the energy efficiency, but the film surface is torn due to the surface collision caused by the external particles, thereby shortening the film life. On the other hand, if it exceeds 1.0 mm, there is a problem that the film thickness is thick and the selective permeation speed of the ions is slowed down, resulting in a decrease in energy efficiency, and furthermore, economical efficiency is lowered.

In one embodiment of the present invention, the solid electrolyte separation membrane of the present invention is an acid-resistant / alkali-resistant amphoteric solid electrolyte separation membrane. In the case of the conventional redox flow cell, since an acidic or basic electrolyte is used as the electrolyte, it is not necessary to use an acid / alkali-resistant ampholyte separator. However, since the battery of the present invention uses an acid and a base as an electrolyte at the same time, a solid electrolyte separation membrane having acid / alkali resistance characteristics is used.

In one embodiment of the present invention, the positive electrode active material applicable to the battery of the present invention is any one selected from the group consisting of Ce, Ni, Co, Mn, V and Fe, preferably Fe, no.

In one embodiment of the present invention, the acidic electrolyte applicable to the battery of the present invention is at least one selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), nitric acid and phosphoric acid, preferably sulfuric acid (H ₂ SO ₄ ) However, the present invention is not limited to the examples, and all acids classified as strong acid electrolytes can be used.

In one embodiment of the present invention, the battery of the present invention is obtained by dissolving a negative electrode active material in a basic electrolyte, and the negative electrode active material is at least one selected from the group consisting of Zn, V and Fe, But is not limited to.

In one embodiment of the invention, the alkaline electrolyte which can be applied to the battery of the present invention from the group consisting of lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium hydroxide (NaOH) and calcium hydroxide (Ca (OH) ₂₎ (KOH), but it is not limited thereto.

In one embodiment of the present invention, the negative electrode active material-positive electrode active material of the present invention is any one or more selected from the group consisting of Zn-Ce, Zn-Ni, Zn-Co, Zn- Negative electrode active material - The positive electrode active material is a redox flow cell which is a Zn-Fe couple. Using Fe, which is a positive electrode active material in acid electrolyte, and Zn, which is a negative electrode active material in a base electrolyte, a voltage of 1.5 V or more and a stack efficiency of 85% or more can be driven. Zn-Ni Electrolyte Integrated Redox Positive and Negative Active Material Couplers that can achieve a stacking efficiency of 85% or more by developing an optimal combination of positive and negative electrode active materials suitable for separating hybrid-electrolyte type systems to be. A solid phase or a dissolved phase such as an oxide or a complex of a reducing agent active material containing Fe ions is dissolved in various aqueous acid solutions to be used as an anode and an aqueous solution in which Zn is dissolved in a strong alkali electrolyte is used as a cathode electrolyte Lt; RTI ID = 0.0 > Zn-Fe < / RTI > Zn is used as an anode active material, and Zn is used as a typical cathode electrode since a voltage of -0.76 V (vs. SHE) in an aqueous acid solution and a voltage of -1.22 V (vs. SHE) are formed in an aqueous alkaline solution.

In one embodiment of the present invention, the battery of the present invention is produced by dissolving a redox cathode active material, which is a strong reducing agent, in an aqueous acid solution to use as an anode electrolyte, and an aqueous solution in which a negative active material is dissolved in a strong alkaline electrolyte, The cathode and anode are separated into a solid electrolyte separator for transferring only specific cations, and the electrolyte is introduced by double injection. In the case of double injection, a separation membrane is essentially used, and it is possible to distinguish the case of using only the acid as the electrolyte, the case of using only the base, and the case of using both the acid and the base. When a single acid or a base electrolyte is used, it is difficult to realize a high voltage. However, in the case of the battery system according to an embodiment of the present invention, since both acid / base electrolytes are used in a dual injection mode, Can be implemented.

In one embodiment of the present invention, the double injection method of the present invention is characterized in that the cathode electrolyte included in the first external reservoir and the anode electrolyte included in the second external reservoir are circulated in the order of injection, redox reaction and recovery into the anode and the anode To a redox flow cell. The negative electrode electrolyte and the positive electrode electrolyte are separately stored in the external reservoir, and are injected from the external reservoir into the negative electrode and the positive electrode, and a redox reaction occurs at the negative electrode and the positive electrode. And a redox flow cell in which the electrolyte is recovered when the oxidation-reduction reaction is terminated.

In one embodiment of the present invention, the bipolar plate of the present invention is at least one selected from the group consisting of gold (Au), platinum (Pt), titanium (Ti), graphite, and carbon composite . In the redox flow cell, the bipolar plate is a plate for separating each cell of the electrode stack. In order to minimize the internal resistance of the cell, conductivity is required, and the electrolyte must be surely blocked from being leaked to the adjacent cell. In addition, the bipolar plate is required to have a stretching property to prevent high mechanical strength (tensile strength) and breakage due to deformation because heat shrinkage or the like may also occur due to pressure and temperature change caused by the electrolyte solution. In order to satisfy the above-mentioned characteristics, any one selected from the group consisting of gold (Au), platinum (Pt), titanium (Ti), graphite and carbon composite is used. , And stretching characteristics can all be used.

In one embodiment of the present invention, the positive electrode and the negative electrode of the present invention are formed of at least one selected from the group consisting of gold (Au), tin (Sn), titanium (Ti), platinum-titanium (Pt-Ti), iridium- Wherein the redox flow cell is at least one selected from the group consisting of a redox flow cell and a redox flow cell. The electrode should have good electrical conductivity and mechanical strength, and be chemically and electrochemically stable. When applied to a battery, it should exhibit high efficiency, be inexpensive, and have a reversible oxidation / reduction reaction with the active material. In consideration of this criterion, it is preferable to use a material selected from the group consisting of gold (Au), tin (Sn), titanium (Ti), platinum-titanium (Pt-Ti), iridium oxide- Any one or more of them may be used without limitation in the case of maintaining stability in an acid and a base. Among them, the carbon material has a low cost, has high chemical resistance in an electrolyte of an acid and a base, and has an advantage of being easy to surface treatment. Particularly, the carbon felt in the carbon material has an advantage of having chemical resistance, stability in a wide voltage range, and high strength. However, since the electrodes are made of only carbon and graphite, it is likely to be broken. As a solution to this problem, polyvinylidene (PVDF), high density polyethylene (HDPE), poly A carbon polymer composite electrode is formed by mixing a binder such as polyvinyl acetate (PVA) or polyolefin with a conductive material such as carbon black or graphite fiber .

In one embodiment of the present invention, the battery system of the present invention comprises a cathode electrolyte including a negative electrode active material; A positive electrode electrolyte (Anolyte) containing a positive electrode active material; electrode; And a solid electrolyte separator for transferring only the positive ions, wherein each of the electrolytes is injected into and recovered from an electrode, circulated, and the positive electrode active material and the negative electrode active material respectively undergo redox reaction. And more particularly, In the battery system, the anode and cathode electrolytes of the storage tank are injected into the anode and the cathode, respectively, which are separated from each other through the pump and the piping. After the redox reaction, the anode and cathode electrolytes are returned to the original storage tank. Each of the electrolytes circulates through the anode and the cathode until the end, and a redox reaction occurs.

In one embodiment of the present invention, the redox flow cell of the present invention comprises a solid electrolyte separator for moving only positive ions, and the solid electrolyte separator is a membrane in which the permeation of the ionic active material is blocked while the migration of cations of Group 1 and Group 2 metals And is excellent in energy efficiency. Here, the cation is a cation of a Group 1 or Group 2 metal, and is preferably at least one selected from the group consisting of Na +, Li + and K +, more preferably K +, but is not limited thereto.

In one embodiment of the present invention, the acidic electrolyte applicable to the battery system of the present invention is at least one selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), nitric acid and phosphoric acid, preferably sulfuric acid (H ₂ SO ₄ ), But not limited to, the acids classified as strong acid electrolytes are all usable.

In one embodiment of the present invention, the battery system of the present invention is obtained by dissolving a negative electrode active material in a basic electrolyte, and the negative electrode active material is at least one selected from the group consisting of Zn, V and Fe, .

In one embodiment of the invention, the alkaline electrolyte which can be applied to the battery system of the present invention is the group consisting of lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium hydroxide (NaOH) and calcium hydroxide (Ca (OH) ₂₎ , Preferably potassium hydroxide (KOH), but it is not limited to examples.

In one embodiment of the present invention, the negative electrode active material-positive electrode active material of the present invention is any one or more selected from the group consisting of Zn-Ce, Zn-Ni, Zn-Co, Zn- Negative electrode active material - The positive electrode active material is a Zn-Fe couple. Fe can be driven at a high voltage of 1.5 V or higher and a stacking efficiency of 85% or more by using Fe, which is a cathode active material in an acid electrolyte, and Zn, an anode active material in a base electrolyte. Zn-Ni electrolyte-integrated redox flow cell, which is a type entirely different from the redox flow cell. Due to the development of optimal transition metal redox anode and anode active material couples suitable for a new type of hybrid electrolyte detachable system, a stacking efficiency of over 85% can be achieved. A solid phase or a dissolution phase such as an oxide or a complex of a reducing agent active material containing Fe ions is dissolved in various acid aqueous solutions to be used as a positive electrode electrolyte and an aqueous solution in which Zn is dissolved in a strong alkali electrolyte is used as a catholyte Lt; RTI ID = 0.0 > Zn-Fe < / RTI > Zn is used as an anode active material, and Zn is used as a typical cathode electrode since a voltage of -0.76 V (vs. SHE) in an aqueous acid solution and a voltage of -1.22 V (vs. SHE) are formed in an aqueous alkaline solution.

Specifically, the voltage for a negative electrode active material-positive electrode active material couple as described above is as follows.

① Zn-Ni couples

Negative electrode: Zn (OH) ₄ ^{2 +} + 2e? Zn (s) + 4OH ^- E ₀ = -1.22V:

The anode: Ni ^{2 +} + 2H ₂ O -> NiO ₂ (s) + 4H ⁺ + 2e E ₀ = -1.77V: Acid

-------------------------------------------------- -------------------------------------

Zn (OH) ₄ ^{2 +} + Ni ²⁺ ? Zn (s) + NiO ₂ (s) + 2H ₂ OE ₀ = -2.99 V

② Zn-Ce couples

Negative electrode: Zn (OH) ₄ ^{2 +} + ² e Zn (s) + ₄ OH ^- E ₀ = -1.22 V

Anode: 2Ce ^{+ 3} → 2Ce ^{+ 4} + 4H ⁺ + 2e E ₀ = -1.61V

-------------------------------------------------- --------------------------------------

Zn (OH) ₄ ^{2 +} + 2Ce ^{3 + -} > Zn (s) + 2Ce ^{4 +} + 4H ₂ OE ₀ = -2.83V

③ Zn-Co couple

Negative electrode: Zn (OH) ₄ ^{2 +} + ² e Zn (s) + ₄ OH ^- E ₀ = -1.22 V

Anode: 2Co ^{2 + -} > 2Co ^{3 +} + 4H ⁺ + 2e E ₀ = -1.82V

-------------------------------------------------- -------------------------------------

Zn (OH) ₄ ^{2 +} + 2Co ^{2 + -} > Zn (s) + 2Co ^{3 +} + 4H ₂ OE ₀ = -3.04V

④ Zn-Mn couple

Negative electrode: Zn (OH) ₄ ^{2 +} + ² e Zn (s) + ₄ OH ^- E ₀ = -1.22 V

Mn ^{5 +} 2H ₂ O MnO ₂ + 4H ⁺ + 2e E ₀ = -1.507 V

-------------------------------------------------- -------------------------------------

Zn (OH) ₄ ^{2 +} + Mn ^{2 + -} & gt ^; Zn (s) + MnO ₂ + 2H ₂ O E ₀ = -2.727 V

⑤ Zn-Fe couple

Negative electrode: Zn (OH) ₄ ^{2 +} + ² e Zn (s) + ₄ OH ^- E ₀ = -1.22 V

Anode: 2Fe ^{2 + -} > 2Fe ^{3 +} + 4H ⁺ + 2e E ₀ = -0.77V

-------------------------------------------------- --------------------------------------

Zn (OH) ₄ ² + 2Fe ^{2 + -} > Zn (s) + 2Fe ³⁺ + 4H ₂ O E ₀ = -1.99 V

In all kinds of batteries using Zn as a cathode, formation of a Zn dendrite structure at the cathode and erosion by the electrolyte of Zn are problems. The formation of a dendritic structure in which Zn is added to the electrode inhibits the stability of the battery due to a short circuit, and the erosion of Zn by the electrolyte is one of the factors of self-discharge. KOH electrolytes are generally used to reduce self-discharge by Zn erosion, but other electrolytes are being sought to replace such KOH, and electrolytes such as NaOH, LiOH or KF are being investigated. However, as a result of using the above-described alternative electrolyte, the result of reducing the erosion of Zn to some extent was obtained, but the performance of the KOH as an electrolyte was not satisfied in the overall battery performance.

The formation of the dendritic structure of Zn is greatly influenced by the flow rate of the electrolyte and the type of current collector. When the electrolyte velocity was more than 15 cm / s, the direction of Zn dendrite growth was along the direction of electrolyte flow, and dendrite growth was inhibited when the cadmium plate was used as a current collector. These results, however, place considerable constraints on the operating and design conditions of the redox flow cell. Inhibition of dendrite structure growth by surface modification of Zn used as an anode active material is a more effective solution. In a conventional Ni-Zn rechargeable battery, the Zn surface was coated with a metal oxide such as TiO ₂ to inhibit Zn dendrite structure formation and to prevent Zn erosion, thereby lowering self-discharge rate. However, the redox flow cell uses various metal electrodes, but in the case of a basic water-based electrolyte, there is no redox couple that takes a voltage more than 1.5 V except for the Zn-Ni electrode. Zn-Ni single electrolyte flow cell was reported in 2007 and used as a supporting electrolyte by adding a high concentration of Zincate solution to KOH. In the charging process, Zn is electrodeposited from the zincate ion at the cathode, Ni (OH) ₂ is oxidized to NiOOH at the anode, and the reaction is reversed during the discharging process. However, the present invention relates to a battery system capable of taking a voltage of 1.5 V or more, which comprises an acidic and basic electrolyte solution, and the electrolytic solution is characterized in that the active material is dissolved. The electronic system includes at least one selected from the group consisting of Zn-Ce, Zn-Ni, Zn-Co, Zn-Mn and Zn-Fe as a negative electrode active material-positive electrode active material couple, , But are not limited to these.

The present invention relates to a battery system and a redox flow battery including the battery system. Unlike the existing battery system, the battery system can realize a high voltage, can be installed at a low cost, can store a large capacity, , A long-time usable battery system, and a redox flow battery including the battery system. In addition, the present invention applies new positive and negative active material couples instead of the positive and negative active material couples used in a single electrolyte. It is a water based system as compared with a non-aqueous Li ion secondary battery, Discharge efficiency can be 85% or more.

Fig. 1 relates to the separation of the battery system according to the injection method of the electrolyte.
2 is a conceptual diagram of a solid electrolyte separation membrane.
3 is a schematic diagram of a battery system according to an embodiment of the present invention.
4 shows the chemical electron orbit stability of the negative electrode active material-positive electrode active material with respect to the use of Zn-Fe.
5 shows a coin cell manufactured by selecting a Zn-Fe redox couple as a negative electrode active material-positive electrode active material couple.
Fig. 6 relates to the efficiency at the time of 1 hour charging at 20 mA / cm < ² > and 2 hours discharging at 10 mA / cm < ^{2 &} gt ;.
Figure 7 relates to the second time during charge and discharge in two hours 10mA / cm ² effective to 10mA / cm ^2.
FIG. 8 is a graph showing the efficiency according to repetition of cycles and efficiency of the battery according to charging and discharging conditions.
Fig. 9 relates to the efficiency when the battery according to Production Example 1 was repeatedly cycled under various discharge conditions and operated up to 50 cycles.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood that these examples are for illustrative purposes only and that the scope of the present invention is not limited by these examples in accordance with the gist of the present invention, will be.

3 is a schematic diagram of a battery system according to an embodiment of the present invention. An example of the redox reaction is the Zn-Fe reaction system. The redox reaction system in which the zinc ions are reduced at the time of charging and the iron ions are oxidized is used. At this time, a solid electrolyte type separation membrane capable of traveling only K + ions is used as the electrolyte separation membrane. The solid electrolyte separator membrane used was stable for a long time in both acidic and basic liquids and was stable even after more than three months in strong acid solution (1 ~ 2M H ₂ SO ₄ ) and strong base solution (4-8M KOH) Therefore, it was confirmed that the phenomenon of water and salt generation caused by the acid-base mixing reaction due to the passage of hydrogen ions during charging / discharging does not occur. The theoretical voltage across the two electrodes is 1.99 V.

Fig. 4 shows the chemical electron orbit stability of the positive electrode active material-negative electrode active material using Zn-Fe. At the time of charging, Zn2 + receives electrons and becomes stabilized by completely filling the 4s orbit. On the other hand, also, two Fe2 + lose electrons and become Fe3 +, which is stabilized by filling the 3d orbit with half. On the contrary, at the time of discharging, Zn ^o lost two electrons to become a state in which the 3d orbit is fully filled and is stable, and Fe 3+ electrons are also obtained and become Fe 2+. Therefore, it is expected that this Fe-Zn RFB system will remain stable even during long-term operation.

Manufacturing example  One

Redox  Manufacture of flow cell

As shown in FIG. 5, a coin cell was formed by selecting a Zn-Fe redox couple as a negative electrode active material-positive electrode active material couple, and the result of charging / discharging experiment was shown. The basic electrolyte is potassium hydroxide (KOH), and the K-Al-Ti-K alloy is used to transport only K +. In this case, Fe is selected as the cathode active material and the acidic electrolyte is sulfuric acid (H ₂ SO ₄ ) P was used as a separator for the solid electrolyte.

Example  One

Redox  Charging and discharging experiment of flow cell

The charging / discharging test results are shown in the graphs of FIGS. 5, the charge / discharge test was performed at a current density of 20 mA / cm ² for 1 hour and at a discharge rate of 10 mA / cm ² for 2 hours. 6 is to measure the efficiency of after 2 hours charge to 10mA / cm ² for 2 hours to discharge 10mA / cm ^2.

According to FIG. 5 and FIG. 6, the efficiency of 75% was obtained when the battery was charged for 1 hour at 20 mA / cm ² and discharged for 2 hours at 10 mA / cm ² . At this time, the charging current is stabilized instantaneously and the charging voltage is very high as 2.4V, so it will be used in future high voltage battery. In addition, the discharge voltage dropped to 1.9 V, which was a net voltage, and then gradually decreased, and was completely discharged at 1.4 V. This result supports the feasibility of using Fe-Zn redox couple as a redox couples for redox flow cells, as a cathode active-anode active material couple.

Referring to Figure 7, 2 hours charge to 10mA / cm ² and the discharge efficiency during 2 hours to 10mA / cm ² represents the 87%. At this time, the charging current is stabilized instantaneously and the charging voltage is very high as 1.99V, which supports the possibility of use in high voltage battery in the future, and the discharging voltage is completely discharged at 1.7V. These results support that Fe-Zn redox couples can be used as redox couples in redox flow cells.

Example  2

Measurement of battery efficiency according to charging and discharging conditions

The efficiency of the battery manufactured in Production Example 1 was measured by repeating charging and discharging cycles.

According to Fig. 8, when the cycle is further turned, the efficiency is stable at 70% or more from 5 cycles. In addition, when the charge / discharge conditions were different, the efficiency was also changed. Especially, the efficiency was more than 85% at 10 mA / cm ^{2 for} 1 hour charge discharge and 5 mA / cm ^{2 for} 2 hours.

Example  3

Measurement of battery efficiency with increasing frequency

The battery efficiency was measured for the case where the battery manufactured in Production Example 1 was repeatedly charged and discharged 50 times under the following discharge conditions.

Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Cm < ² > for 1 hour and discharged at 5 mA / cm < ² > for 1 hour 1 hour charge to 10mA / cm ² and 21 hours discharge with 10mA / cm ² 1 hour charge to 30mA / cm ² and 1 hours discharged to 30mA / cm ² 1 hour charge to 50mA / cm ² and 1 hours discharged to 50mA / cm ²

FIG. 9 shows a stable efficiency of 70% or more under all conditions even when the cycle is operated up to 50 cycles under the discharge condition shown in Table 1 above. The efficiencies varied with charge and discharge conditions, especially at 5 mA / cm ² and 10 mA / cm ^{2 for} 1 hour charging and discharging conditions.

Claims (17)

A first external reservoir comprising a positive electrode electrolyte comprising an acidic electrolyte;
A second external reservoir including a negative electrode electrolyte including a basic electrolyte;
electrode;
A solid electrolyte separator for moving only cations; And
A bipolar plate,
Wherein the acidic electrolyte comprises a cathode active material,
The basic electrolyte includes a negative electrode active material,
Wherein the negative electrode and the positive electrode electrolyte are injected into the negative electrode and the positive electrode by a double injection method. The method according to claim 1,
Wherein the solid electrolyte separation membrane moves at least one selected from the group consisting of Li +, Na +, and K +. The method according to claim 1,
Wherein the solid electrolyte separation membrane has a void volume of 30 to 70%, a pore size of 0.05 to 0.1 탆, and a thickness of 0.3 to 1.0 mm. The method according to claim 1,
Wherein the acidic electrolyte comprises at least one selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), nitric acid, and phosphoric acid. The method according to claim 1,
Wherein the basic electrolyte comprises at least one selected from the group consisting of lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium hydroxide (NaOH), and calcium hydroxide (Ca (OH) ₂ ). The method according to claim 1,
Wherein the anode active material and the cathode active material are any one or more selected from the group consisting of Zn-Ce, Zn-Ni, Zn-Co, Zn-Mn and Zn-Fe. The method according to claim 6,
The negative electrode active material-positive electrode active material is a Zn-Fe couple. The method according to claim 1,
Wherein the anode electrolyte included in the first external storage tank and the anode electrolyte included in the second external storage tank circulate in the order of injection, redox reaction and recovery in the order of the anode and the anode. The method according to claim 1,
Wherein the bipolar plate is at least one selected from the group consisting of gold (Au), platinum (Pt), titanium (Ti), graphite, and carbon composite. The method according to claim 1,
The electrode may be at least one selected from the group consisting of gold (Au), tin (Sn), titanium (Ti), platinum-titanium (Pt-Ti), iridium- Flow cell. Catholyte comprising a negative electrode active material;
A positive electrode electrolyte (Anolyte) containing a positive electrode active material;
electrode; And
And a solid electrolyte separator for moving only the cation,
12. The redox flow cell according to any one of claims 1 to 12, wherein each of the electrolytes is injected into and recovered from an electrode and circulated, and the cathode active material and the anode active material respectively undergo redox reaction The battery system. 12. The method of claim 11,
Wherein the solid electrolyte separation membrane moves at least one selected from the group consisting of Li +, Na +, and K +. 12. The method of claim 11,
Wherein the positive electrode electrolyte comprises an acidic electrolyte,
Wherein the negative electrode electrolyte comprises a basic electrolyte. 14. The method of claim 13,
Wherein the acidic electrolyte comprises at least one selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), nitric acid, and phosphoric acid. 14. The method of claim 13,
Wherein the basic electrolyte comprises at least one selected from the group consisting of lithium hydroxide (LiOH), potassium hydroxide (KOH), sodium hydroxide (NaOH) and calcium hydroxide (Ca (OH) ₂ ). 12. The method of claim 11,
Wherein the anode active material and the cathode active material are at least one selected from the group consisting of Zn-Ce, Zn-Ni, Zn-Co, Zn-Mn and Zn-Fe. 12. The method of claim 11,
Wherein the negative electrode active material-positive electrode active material is a Zn-Fe couple.

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