Electrolyte containing vanadium ions and vanadium ion battery containing electrolyte

Abstract

The present invention relates to an electrolyte solution containing vanadium ions and a vanadium ion battery containing the electrolyte solution, and more particularly, to an electrolyte solution containing vanadium ions in which the oxidation value of the vanadium ions is adjusted, and a vanadium ion battery containing the electrolyte solution, and to a vanadium ion battery containing the electrolyte solution. The purpose of the present invention is to improve a decrease in charge energy (capacity) caused by a concentration deviation phenomenon of an electrolyte solution containing vanadium ions in a positive electrode and a negative electrode when a vanadium ion battery to which the electrolyte solution containing vanadium ions is applied is charged / discharged.

Description

Technical Field

[0001] The present invention relates to an electrolyte containing vanadium ions and a vanadium ion battery containing the electrolyte, and more specifically, to an electrolyte and a vanadium ion battery containing the electrolyte, wherein the electrolyte contains vanadium ions with an adjusted oxidation number (oxidation number) of the vanadium ions so as to improve the phenomenon of reduced charging energy (capacity) caused by concentration deviation of the electrolyte containing vanadium ions in the positive electrode and the negative electrode when the vanadium ion battery using the electrolyte containing vanadium ions is charged / discharged. Background Art

[0002] Unlike conventional secondary batteries, a redox flow battery (RFB), which is a type of oxidation / reduction secondary battery, is a system in which active materials in an electrolyte are oxidized / reduced to perform charge / discharge, and is an electrochemical power storage device that stores electrical energy as chemical energy of an electrolyte.

[0003] The electrolyte of the oxidation / reduction secondary battery uses a substance with a redox couple. The electrolyte of the oxidation / reduction secondary battery originally used redox pairs of different substances in the positive and negative electrodes, but there may be a problem of a reduction in the capacity of the battery due to the crossover of the ionized different substances through the diaphragm during charge and discharge. As an example, for the crossover phenomenon, the degree and speed of vanadium ion movement may vary depending on the type of diaphragm, which may affect the vanadium ion concentration deviation phenomenon.

[0004] To this end, as a method for alleviating the ion crossover phenomenon, a method of applying vanadium to both the positive and negative electrodes has been proposed. Since the electrolyte containing vanadium ions is an aqueous electrolyte, it has the advantages of not only high stability against explosion, etc., but also increased battery life when applied to secondary batteries, and has thus been used until recently.

[0005] An electrolyte containing vanadium ions using vanadium ions as an active material has the longest life in an oxidation / reduction secondary battery and is advantageous in terms of increasing capacity. In addition, the electrolyte can be separated and reused through the electrochemical reaction of charging / discharging the secondary battery, which has an advantage in terms of cost.

[0006] The electrolyte containing vanadium ions used in the positive and negative electrodes requires vanadium compounds with oxidation values ​​of tetravalent (4+) at the positive electrode and trivalent (3+) at the negative electrode, respectively, based on the fully discharged state, and vanadium compounds with oxidation values ​​of pentavalent (5+) at the positive electrode and divalent (2+) at the negative electrode, based on the fully charged state. The charge / discharge reaction occurs as the oxidation value of the vanadium active material changes. In order to produce an electrochemical reversible reaction, it is important to manufacture according to the oxidation value of the vanadium ions in the positive and negative electrolytes.

[0007] The positive electrode and the negative electrode receive the positive electrode oxidation / reduction pair (V 4+ / V 5+ ) and the negative electrode oxidation / reduction couple (V 2+ / V 3+ ) is driven by the dissolved electrolyte solution (electrolyte), and the following half reactions occur respectively.

[0008] Positive half reaction: V 5+ +e － ←→V 4+

[0009] Negative half reaction: V 2+ ←→V 3+ +e －

[0010] Generally, as an electrolyte containing vanadium ions, an electrolyte having a vanadium oxidation number of 3.50 (3.5+) which can be used in both the electrolyte supplied to the negative electrode and the electrolyte supplied to the positive electrode has been used.

[0011] However, when an electrolyte solution having a vanadium oxide value of 3.50 is used as in the conventional method, the concentration of vanadium ions in the positive and negative electrodes deviates more and more as charge / discharge is repeated, thereby causing a problem such as a decrease in charge energy (capacity).

[0012] Specifically, when a redox secondary battery using an electrolyte containing vanadium ions is charged, a concentration deviation phenomenon occurs in which the vanadium ion concentration of the negative electrode decreases and the vanadium ion concentration of the positive electrode increases. As a result, the charging energy decreases, resulting in a decrease in energy density, and as a result, the life and efficiency of the redox secondary battery also decrease, which may lead to reduced performance. Summary of the invention

[0013] An object of the present invention is to provide an electrolyte solution containing vanadium ions with adjusted oxidation values, so as to alleviate the problem of reduced performance of oxidation / reduction secondary batteries, in particular, reduced charging energy (capacity).

[0014] Another object of the present invention is to provide a vanadium ion battery driven by supplying the electrolyte solution containing vanadium ions of the present invention as a redox secondary battery with a significantly reduced volume by eliminating the conventional electrolyte tank and fluid pump.

[0015] The subject of the present invention is not limited to the above-mentioned object, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

[0016] In one embodiment of the present invention, a vanadium ion battery (VIB) may include one or more vanadium ion battery units, and the vanadium ion battery units may include: a positive electrode collector; a negative electrode collector, which is separated from the positive electrode collector; a diaphragm, which is arranged between the positive electrode collector and the negative electrode collector; a positive electrode electrolyte container, which is formed between the positive electrode collector and the diaphragm; and a negative electrode electrolyte container, which is formed between the negative electrode collector and the diaphragm, and an electrolyte containing vanadium ions is supplied to the positive electrode electrolyte container as a positive electrode electrolyte, and an electrolyte containing vanadium ions is supplied to the negative electrode electrolyte container as a negative electrode electrolyte, and the electrolyte containing vanadium ions may contain vanadium ions having an oxidation value greater than 3.50 and less than 4.00 and an acidic solution.

[0017] The oxidation number of the electrolyte containing vanadium ions may be greater than 3.50 and less than 3.80.

[0018] The vanadium ions in the electrolyte containing vanadium ions can be provided by vanadium oxide.

[0019] The vanadium oxide may include V 2 O 5 、VOSO 4 、V 2 O 3 NH 4 VO 3 and V 2 O 4 One or more of the following.

[0020] The acidic solution may include one or more of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid.

[0021] The vanadium ion battery cell may further include a migration portion connecting the positive electrode electrolyte container and the negative electrode electrolyte container.

[0022] The positive electrode current collector may include a positive electrode metal current collector and a positive electrode carbon current collector, and the negative electrode current collector may include a negative electrode metal current collector and a negative electrode carbon current collector.

[0023] The vanadium ion battery cell may further include: a positive solid electrode disposed in the positive electrolyte container and impregnated with the positive electrolyte; and a negative solid electrode disposed in the negative electrolyte container and impregnated with the negative electrolyte.

[0024] The membrane may be a hydrocarbon-based membrane including a hydrocarbon-based polymer.

[0025] The hydrocarbon-based membrane may be a membrane formed of the hydrocarbon-based polymer, or may be a membrane formed by coating the hydrocarbon-based polymer on one or both surfaces of a substrate.

[0026] The hydrocarbon-based polymer may be a cation-conductive hydrocarbon-based polymer.

[0027] The hydrocarbon-based polymer may include any one or more of a polyimide-based polymer, a polyetheretherketone-based polymer, a polyethersulfone-based polymer, and a polybenzimidazole-based polymer.

[0028] The electrolyte solution containing vanadium ions of the present invention can be provided in a state where the oxidation number exceeds 3.50.

[0029] When the electrolyte containing vanadium ions having an oxidation number exceeding 3.50 of the present invention is applied to a secondary battery, the phenomenon of reduced charging energy (capacity) caused by the deviation of vanadium ion concentration between the positive electrode and the negative electrode during charge / discharge of the vanadium ion battery can be improved.

[0030] When the electrolyte containing vanadium ions of the present invention is applied, the energy density of the vanadium ion battery can be significantly increased, and it is beneficial to improve the efficiency and life of the vanadium ion battery. This is because, even if the battery with high energy density is charged with the same amount of energy, the state of charge (SoC) is relatively low, the potential difference between the positive electrode and the negative electrode becomes smaller, so the possibility of irreversible reactions such as hydrogen generation becomes smaller, and even if the battery with high energy density releases the same amount of energy, it will use less depth of discharge (DoD), so it has the advantages of longer long-term battery life and being able to use a more efficient range.

[0031] The vanadium ion battery of the present invention is designed to eliminate the electrolyte storage tank and electrolyte flow fluid pump of the conventional redox flow battery (RFB), so it has an advantage in ensuring space when manufactured into a large energy storage system (ESS).

[0032] The electrolyte containing vanadium ions of the present invention has a higher energy density than the case of using a conventional 3.50-valent vanadium electrolyte, and thus has an advantage that the size of an aqueous secondary battery using the electrolyte can be further reduced.

[0033] When the electrolyte solution containing vanadium ions of the present invention is used, the effect of improving the decrease in charging energy (capacity) can be further enhanced in a vanadium ion battery having a sealed structure.

[0034] The effects of the present invention are not limited to the effects mentioned above, and those skilled in the art can clearly understand other effects not mentioned from the description of the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 FIG. 1 is an exploded perspective view of a vanadium ion battery unit cell according to an embodiment of the present invention.

[0036] Figure 2 FIG. 1 is a perspective view of a vanadium ion battery unit cell according to an embodiment of the present invention.

[0037] Figure 3 yes Figure 2 A cross-sectional view of the vanadium ion battery cell along direction 3-3 is shown.

[0038] Figure 4 This is a perspective view schematically showing the structure of a vanadium ion battery in a state where vanadium ion battery cells are stacked according to an embodiment of the present invention.

[0039] Figure 5 FIG. 1 is a titration curve for confirming the oxidation value of an electrolyte solution containing vanadium ions according to an embodiment of the present invention.

[0040] Description of Reference Numerals

[0041] 130a: Positive electrode collector

[0042] 130b: Negative electrode collector

[0043] 131a: Positive metal collector

[0044] 131b: Negative electrode metal collector

[0045] 132a: Positive electrode carbon collector

[0046] 132b: Negative carbon current collector

[0047] 110: Support

[0048] 111a: positive electrode electrolyte storage part

[0049] 111b: Negative electrode electrolyte storage part

[0050] 112: Migration Department

[0051] 120: Diaphragm

[0052] 150a: Positive solid electrode

[0053] 150b: Negative solid electrode

[0054] 100: Vanadium ion battery cell

[0055] 100c: Partial protrusion in the metal current collector

[0056] 200: Busbar

[0057] 300: End plate

[0058] 1000: Vanadium ion battery DETAILED DESCRIPTION

[0059] The advantages, features and methods for achieving the advantages and features of the present invention can be more clearly understood by referring to the accompanying drawings and the embodiments described in detail below. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various ways. This embodiment is only for the purpose of more completely disclosing the present invention, so as to more completely indicate the scope of the present invention to those skilled in the art to which the present invention belongs. The present invention is limited only by the scope of the claims. The same reference numerals throughout the specification represent the same constituent elements.

[0060] When explaining this specification, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

[0061] In this specification, although the first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from other components. Unless otherwise specified, the first component may be the second component.

[0062] Throughout the specification, unless otherwise specified, each constituent element may be in the singular or in the plural.

[0063] When explaining the constituent elements in this specification, even if there is no additional explicit description, it can be interpreted that the components include a range of error.

[0064] In the present specification, an arbitrary structure is arranged on the "top (or bottom)" of a constituent element or on the "top (or bottom)" of a constituent element, which may not only mean that the arbitrary structure is arranged in contact with the top surface (or bottom surface) of the constituent element, but also mean that other structures may be provided between the constituent element and the arbitrary structure arranged on (or below) the constituent element.

[0065] In this specification, it should be understood that if any constituent element is recorded as being "connected", "combined" or "contacting" another constituent element, the constituent elements may be directly connected or in contact, or other constituent elements may be "disposed" between the constituent elements, or the constituent elements may be "connected", "combined" or "contacting" each other through other constituent elements.

[0066] When “including,” “having,” “configuring,” “configuring,” “having,” etc. are used for constituent elements in this specification, other components may be added unless “only” is used. When a constituent element is expressed in the singular, the plural number is included unless otherwise specified.

[0067] Throughout the specification, when described as "A and / or B", unless otherwise specified, it means A, B, or A and B, and when described as "C to D", unless otherwise specified, it means C or more and D or less.

[0068] In this specification, unless otherwise specified, all units are interpreted as "weight".

[0069] In this specification, unless there is a specific statement to the contrary, "an electrolyte containing vanadium ions" is interpreted as referring to the same object as "a vanadium ion electrolyte", "an electrolyte using (utilizing) vanadium ions", "an electrolyte containing vanadium oxide", "a vanadium electrolyte", "an electrolyte containing a vanadium active material", etc.

[0070] In this specification, the oxidation value of vanadium ions in a vanadium ion electrolyte can be the oxidation value of the electrolyte itself during manufacture or supply or the average value of the oxidation value of the electrolyte supplied to the positive and negative electrodes. When the secondary battery is driven by charge / discharge, it can represent the average value of the oxidation values ​​of the positive electrode electrolyte and the negative electrode electrolyte.

[0071] <Electrolyte containing vanadium ions>

[0072] Hereinafter, an electrolyte solution containing vanadium ions according to one embodiment of the present invention will be described in detail.

[0073] In the past, in the oxidation / reduction secondary battery using the electrolyte containing vanadium ions, the vanadium electrolyte with an oxidation value of 3.50 was used, but especially in the case of multiple charge / discharge of hundreds or thousands of times of the secondary battery, the deviation of the vanadium ion concentration of the vanadium electrolyte injected into the positive and negative electrodes gradually became serious, and the performance of the secondary battery such as the reduction of the charging energy (capacity) was reduced. The inventors confirmed the following through experiments and came up with the present invention: if a vanadium electrolyte with an oxidation value exceeding 3.50 is used instead of the vanadium electrolyte with an oxidation value of 3.50 used in the past, even if the vanadium ion concentration is deviated, the reduction of the charging energy (capacity) that occurs when the oxidation / reduction secondary battery is repeatedly charged / discharged can be eliminated.

[0074] As described above, the electrolyte containing vanadium ions of the present invention comprises vanadium ions and an acidic solution, wherein the oxidation value of the vanadium ions exceeds 3.50, and the effect of solving the problem of reduced charging energy can be shown. In particular, the effect is further increased as the number of charge and discharge cycles increases.

[0075] Specifically, it can be confirmed by experiment that the electrolyte with a vanadium ion oxidation value exceeding 3.50 valences is compared with the previous electrolyte with a vanadium ion oxidation value of 3.50 valences, and in several charge / discharges, the charging energy is slightly decreasing, but with repeated charging / discharging for tens or hundreds of times, the charging energy increases instead. In view of the fact that redox secondary batteries are usually driven hundreds or thousands of times by charge / discharge, the experimental results of the present invention can be interpreted as being very significant results. In particular, since the electrolyte comprising vanadium ions of the present invention can improve energy density, the size of the redox secondary battery using an aqueous electrolyte as in the present invention can be significantly reduced, and the efficiency and life of the redox secondary battery can be improved.

[0076] On the other hand, if the oxidation number of the vanadium ion in the electrolyte is less than 3.50, the charging energy decreases not only in a few charge / discharge cycles but also further decreases even after dozens or hundreds of charge / discharge cycles.

[0077] On the contrary, if the oxidation value of the vanadium ion increases too much, the effect of alleviating the reduction in the charging energy will be reduced again. For example, the oxidation value of the vanadium ion can be lower than 4.00, for example, the oxidation value of the vanadium ion can be lower than 3.70, for example, the oxidation value of the vanadium ion can be lower than 3.65, but this can vary depending on the movement path of the vanadium ion.

[0078] According to one embodiment of the present invention, the vanadium ions in the vanadium electrolyte of the present invention can be provided by vanadium oxides, for example, can include vanadium ions selected from V 2 O 5 、VOSO4 、V 2 O 3 NH 4 VO 3 and V 2 O 4 At least one or more of the group of components may be selected, but not necessarily limited thereto, according to production conditions of the electrolyte, production target amount, and the like.

[0079] According to an embodiment of the present invention, the supply form of the vanadium oxide does not need to be particularly limited, but, for example, in terms of process efficiency, it may be a powder type.

[0080] According to an embodiment of the present invention, the acidic solution may include one or more selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, but, for example, a sulfuric acid solution may be used.

[0081] The concentration of the acidic solution may be, for example, 0.1M to 10M, for example, 1M to 8M, for example, 2M to 5M, but is not necessarily limited thereto and may be appropriately adjusted according to the type of the selected acidic solution, etc.

[0082] The concentration of vanadium ions of the electrolyte containing vanadium may be 1.5M to 3.0M.

[0083] <Vanadium ion battery>

[0084] Hereinafter, a vanadium ion battery according to another embodiment of the present invention will be described in detail.

[0085] Due to the electrolyte storage tank and electrolyte flow fluid pump of the existing redox flow battery (RFB), the overall size of the redox flow battery using vanadium electrolyte becomes very large, so there are limitations caused by space restrictions and design difficulties. For this reason, in the present invention, a vanadium ion battery (VIB) as a redox secondary battery with a closed structure is used, and the electrolyte tank and fluid pump are removed. Specifically, in order to circulate the inside of the battery itself without a pump, it is designed to stack one or more units (unit cell), which include: a positive electrode collector; a negative electrode collector, which is separated from the positive electrode collector; a diaphragm, which is arranged between the positive electrode collector and the negative electrode collector; as a result, compared with the previous redox secondary battery, the power density can be increased by up to 2 to 50 times, and the stability of energy output can be improved.

[0086] A vanadium ion battery according to an embodiment of the present invention may include one vanadium ion battery unit or two or more vanadium ion battery units, for example, three or more vanadium ion battery units. For example, after being stacked as described above, the stacked units may be additionally electrically connected in parallel.

[0087] Reference Figures 1 to 3 , detailing the vanadium ion battery cell.

[0088] The vanadium ion battery cell 100 of the present invention includes: a positive electrode collector 130a; a negative electrode collector 130b, which is separated from the positive electrode collector; a diaphragm 120, which is arranged between the positive electrode collector 130a and the negative electrode collector 130b; a positive electrode electrolyte container 111a, which is formed between the positive electrode collector 130a and the diaphragm 120; and a negative electrode electrolyte container 111b, which is formed between the negative electrode collector 130b and the diaphragm 120.

[0089] The positive electrode collector 130a and the negative electrode collector 130b of the vanadium ion battery cell 100 can be manufactured by stacking metal collectors 131a, 131b and carbon collectors 132a, 132b, respectively. The metal collectors 131a, 131b are formed of a metal with high conductivity (for example, copper or aluminum) and can be connected to a busbar for electrically connecting each unit. The carbon collectors 131a, 131b are formed of materials such as graphite, carbon, and carbon plastic, and can be formed into collectors with high conductivity and high acid resistance. The metal collectors 131a, 131b and the carbon collectors 132a, 132b can be formed into quadrilateral plates.

[0090] The vanadium ion battery cell 100 may include a support 110 for disposing a separator 120 between the positive electrode current collector 130a and the negative electrode current collector 130b, and for providing a space for the positive electrode electrolyte container 111a and the negative electrode electrolyte container 111b. The support 110 may be attached to the carbon collectors of the positive electrode current collector 130a and the negative electrode current collector 130b, and a closed structure is formed due to the above-mentioned construction, thereby being able to ensure the airtightness required for the vanadium ion battery.

[0091] The positive electrode electrolyte container 111a and the negative electrode electrolyte container 111b may be supplied with an electrolyte containing vanadium ions as the positive electrode electrolyte and the negative electrode electrolyte, respectively. The supplied electrolyte is an electrolyte containing vanadium ions in one embodiment of the present invention, which may contain vanadium ions having an oxidation value of more than 3.50 and less than 4.00 and an acidic solution. According to one embodiment, it may contain vanadium ions having an oxidation value of more than 3.50 and less than 3.80.

[0092] According to an embodiment of the present invention, the vanadium ion battery unit 100 may include a migration portion 112 connecting the positive electrode electrolyte container and the negative electrode electrolyte container. The migration portion 112 may be formed on the support member 110.

[0093] The migration part 112 is used to eliminate the ionized substances (vanadium ions, ionized H 2 O, ions in an acidic aqueous solution, etc.) cross each other through the diaphragm 120, causing an imbalance.

[0094] More specifically, during repeated charge / discharge, the volume of the electrolyte contained in the positive electrode electrolyte container 111a and the negative electrode electrolyte container 111b may change. When charging the vanadium ion battery, some ions (ionized H 2 O, vanadium ions, SO 4 2－ In addition, the divalent vanadium ions present in the negative electrode electrolyte container strongly attract the ionized H 2 The force of O may cause the volume of the negative electrode electrolyte to increase. As a result, the vanadium ion concentration at the negative electrode may decrease, while the vanadium ion concentration at the positive electrode may increase.

[0095] As described above, when charging / discharging is repeated, an imbalance in the volume change of the negative electrode electrolyte and the positive electrode electrolyte occurs. Therefore, in the present invention, the imbalance in the volume of the electrolyte can be eliminated by moving the electrolyte from the electrolyte containing part with a relatively increased volume to the electrolyte containing part with a reduced volume using the migration part 112.

[0096] On the other hand, when an oxidation / reduction secondary battery using an electrolyte containing vanadium ions is discharged, water, vanadium ions, anions contained in the acidic solution of the electrolyte (for example, HSO in the case of sulfuric acid) 4 － ) can move from the negative electrode electrolyte to the positive electrode electrolyte through the migration portion 112, and as a result, the phenomenon that the vanadium concentration of the negative electrode electrolyte decreases and the vanadium concentration of the positive electrode electrolyte increases will be further aggravated.

[0097] As described above, in the vanadium ion battery (VIB) of the present invention, the reduction in energy density caused by the imbalance of vanadium concentrations in the positive and negative electrolytes during charge / discharge can be eliminated by using the electrolyte containing vanadium ions according to one embodiment of the present invention.

[0098] Furthermore, as the vanadium ion battery is repeatedly charged and discharged, the charging energy is improved compared to the conventional electrolyte using 3.50-valent vanadium ions, resulting in an improvement in the efficiency and life of the vanadium ion battery and a reduction in the volume of the vanadium ion battery.

[0099] On the other hand, according to one embodiment of the present invention, the vanadium ion battery cell 100 may also include: a positive solid electrode 150a, arranged in the positive electrolyte container 111a, and impregnated with the positive electrolyte; and a negative solid electrode 150b, arranged in the negative electrolyte container 111b, and impregnated with the negative electrolyte.

[0100] The positive solid electrode 150a and the negative solid electrode 150b can be impregnated with the positive electrolyte and the negative electrolyte, respectively, and arranged in the positive electrolyte container 111a and the negative electrolyte container 111b. The positive solid electrode 150a and the negative solid electrode 150b can include carbon or graphite felt, carbon fiber, carbon black, graphite powder or graphene and other carbon-based materials. The positive solid electrode 150a can be in close contact with the positive collector 130a and the separator 120, and the negative solid electrode 150b can be in close contact with the negative collector 130b and the separator 120.

[0101] Regarding the phenomenon that vanadium ions in the vanadium electrolyte cross each other through the diaphragm of the vanadium ion battery, the degree and speed of vanadium ion movement may vary depending on the type of diaphragm, which may affect the vanadium ion concentration deviation phenomenon. Therefore, the diaphragm 120 of the vanadium ion battery unit 100 of the present invention may include a hydrocarbon diaphragm containing a cation conductive hydrocarbon polymer. It is made of fluorine-based cationic conductive polymers, so its disadvantage is that halogen substances may flow out and be easily contaminated by secondary batteries. In addition, in aqueous secondary batteries, protons (H + ) during movement and the side reactions that often occur in aqueous secondary batteries (producing H 2 , CO 2 Gases such as ions may cause pressure to be generated inside the cell. Therefore, in a vanadium ion battery (VIB) having a closed structure, it is necessary to have excellent mechanical strength to withstand the pressure as described above, and to have high stability to prevent irreversible and side reactions. Moreover, even if it is immersed in an acidic electrolyte for a long time, it is necessary to further ensure excellent acid resistance, so it is preferred to use a hydrocarbon-based diaphragm.

[0102] The hydrocarbon-based membrane may be formed of the hydrocarbon-based polymer, or may be formed by coating the hydrocarbon-based polymer on a substrate. For example, the coating may be performed by immersing one or both sides of a porous substrate in a solution in which the hydrocarbon-based polymer is dissolved in a solvent and then drying.

[0103] The porous substrate may be selected from a substrate that exhibits high tensile strength (e.g., 100 MPa or more) even at a relatively thin thickness and has excellent impregnation properties with hydrocarbon-based polymers and coating properties after drying. For example, a porous substrate made of polypropylene (PP) or polyethylene (PE) may be selected, but is not necessarily limited thereto.

[0104] The hydrocarbon-based polymer may include any one of a polyimide-based polymer, a polyetheretherketone-based polymer, a polyethersulfone-based polymer, and a polybenzimidazole-based polymer.

[0105] Reference Figure 4 The vanadium ion battery 1000 of the present invention can be manufactured by stacking a plurality of vanadium ion battery units 100. The plurality of vanadium ion battery units 100 can be electrically connected via a busbar 200. The plurality of vanadium ion battery units 100 can be electrically connected to the busbar 200 via a portion of the protrusions 100c in the metal current collectors 131a and 131b.

[0106] A pair of end plates 300 are disposed at the upper and lower ends of the plurality of vanadium ion battery cells 100. The end plates 300 are made of a relatively strong insulating material or a metal material that has been subjected to an insulating treatment.

[0107] The bus bar 200 transmits electricity generated from the plurality of cells 100 to the outside during discharge, and transmits external electricity to the plurality of cells 100 during charge. The bus bar 200 may connect the plurality of cells 100 in parallel or in series. The bus bar 200 may be configured to cover one side of the plurality of cells 100 and one side of the pair of end plates 300.

[0108] The following describes the manufacturing examples and experimental examples of the present invention and further describes the present invention in detail. However, this is only one embodiment of the present invention and the present invention is not limited thereto.

[0109] Production Example 1: Production of an Electrolyte Containing Vanadium Ions

[0110] The stirrer was placed in a heating mantle heated to about 80°C, and then three-stage distilled water (DI water; DW) prepared by a three-stage ultrapure water device, 98% sulfuric acid (H 2 SO 4 ) and 99.5% oxalic acid as a reducing agent, and then a small amount of V 2 O 5 powder.

[0111] At this time, in order to prepare 1L of vanadium electrolyte, 98% H 2 SO 4 236mL and 99.5% oxalic acid 108g, DW780mL were mixed, and 154g of V was added to prepare a 1.7M vanadium ion electrolyte. 2 O 5 Then, the mixture was heated at about 80°C and stirred for about 12 hours.

[0112] Vanadium was fully dissolved in sulfuric acid to prepare a vanadium electrolyte with an oxidation value of 4. The vanadium electrolyte with an oxidation value of 4 was then injected into a VRFB unit (manufactured by Standard Energy) for electrochemical reduction, and then reduced at the negative electrode to prepare vanadium ion electrolytes with valences of 3.45, 3.50, 3.55, 3.60, 3.65, 3.70, 3.75, and 3.80, respectively.

[0113] At this time, the oxidation value of the manufactured vanadium ion electrolyte may be calculated according to the following Formula 1 based on a titration method using an oxidant.

[0114] <Formula 1> Average oxidation number of vanadium ion electrolyte = 5-{V b / (V b -V a )}

[0115] In the above formula 1, V a The amount of oxidant consumed when the oxidation value of the vanadium electrolyte is oxidized from more than 3.00 to 4.00 (mL), V b It indicates the amount (mL) of oxidant consumed when the oxidation number of the vanadium electrolyte solution is oxidized from over 3.00 to 5.00.

[0116] like Figure 5 As shown in FIG. 1 , if an oxidant is added to a vanadium electrolyte having an oxidation value of 3.00, and the relative potential value (V) relative to Ag / AgCl as a reference electrode is measured, and a first-order derivative curve is drawn after drawing a titration curve of the vanadium electrolyte, there are two inflection points represented by peaks. At this time, the inflection points represent the points where the oxidation value state of the vanadium electrolyte changes, i.e., the equivalent points. Based on the inflection points, it can be confirmed that the amount (mL) of the oxidant consumed when the oxidation value of the vanadium electrolyte is oxidized from more than 3.00 to 4.00 can be determined. a And the amount of oxidant consumed when the oxidation value of the vanadium electrolyte is oxidized from more than 3.00 to 5.00 (mL) V b , (V b -V a ) represents the amount of oxidant consumed (mL). Figure 5In the figure, potential (V, relative to Ag / AgCl) represents the relative potential value (V) relative to Ag / AgCl as a reference electrode, and ΔV / ΔmL represents the value differentiated by the change in potential value (ΔV) relative to the volume (ΔmL) of the consumed oxidant.

[0117] In the present invention, 0.02M KMnO 4 As the oxidant, Figure 5 The results confirmed in V a is 1.6 (mL), V b It is 4.8 (mL), so according to the above formula 2, 5-{4.8 / (4.8-1.6)}=3.5, and it can be known that the oxidation number is 3.5.

[0118] According to the titration method described above, the oxidation value of the vanadium electrolyte solution prepared above can be measured.

[0119] Manufacturing Example 2: Manufacturing of a vanadium ion battery

[0120] Two current collectors were prepared by stacking a carbon current collector (graphite composite material, thickness: 0.2 mm) and a metal current collector (aluminum foil, thickness: 0.2 mm), and used as a positive electrode current collector and a negative electrode current collector, respectively.

[0121] A cation exchange membrane (thickness: 20 μm, Standard Energy) made by coating m-PBI (poly[2,2-(m-phenylene)-5,5bibenzimidazole]) on a polyethylene (PE) substrate was used as a diaphragm (hereinafter referred to as “PBI diaphragm”).

[0122] After preparing a hollow square support, a positive electrode collector and a negative electrode collector are arranged on both sides of the support, and the PBI separator is arranged in the center of the support to separate the positive electrode collector and the negative electrode collector to form a positive electrode electrolyte container and a negative electrode electrolyte container. A migration part connecting the positive electrode electrolyte container and the negative electrode electrolyte container is formed on the support to manufacture a vanadium ion battery cell.

[0123] Experimental example: Charging / discharging experiment of vanadium ion battery

[0124] In order to confirm the charging energy performance of the vanadium ion electrolyte of each oxidation number during charge / discharge, the vanadium ion electrolyte with an oxidation number of 3.50 manufactured in Manufacturing Example 1 was put into the positive and negative electrodes of the vanadium ion battery manufactured in Manufacturing Example 2.

[0125] As the charge / discharge driving conditions, the battery was charged to 1.70 V at a constant current of 0.5 C, and discharged to 1.10 V at a constant current of 0.5 C in the same manner as the charge.

[0126] The charging / discharging was performed 500 times (cycles) under the charging and discharging conditions described above, and the charging energy (wh) was calculated at 5, 100, 200, 300, 400, and 500 times, respectively. The charging energy is a value calculated by integrating the value of the charging voltage measured at the sampling time during battery charging multiplied by the charging current (0.5C).

[0127] Then, the vanadium ion electrolytes with oxidation values ​​of 3.45, 3.55, 3.60, 3.65, 3.70, 3.75 and 3.80 were similarly charged / discharged up to 500 times (cycles), and the charging energy was measured at 5, 100, 200, 300, 400 and 500 times, respectively.

[0128] Taking the vanadium ion electrolyte with an oxidation value of 3.50 as a benchmark, the increase and decrease rates (percentages; %) of the charging energy of vanadium ion electrolytes with oxidation values ​​of 3.45, 3.55, 3.60, 3.65, 3.70, 3.75 and 3.80 were calculated according to Formula 2 and are listed in Table 1 below.

[0129] <Equation 2> The rate of increase or decrease of charging energy: {(E x -E 3.5 ) / E 3.5}×100(%)

[0130] In Formula 2, E 3.5 is the charging energy of the vanadium ion electrolyte with an oxidation number of 3.50, E x It refers to the charging energy of vanadium ion electrolyte with an oxidation number other than 3.50.

[0131] [Table 1]

[0132]

[0133] As can be seen from Table 1 above, starting from the 200th charge / discharge cycle, the increase / decrease rate of the charging energy of the vanadium electrolyte with an oxidation value exceeding 3.50 is calculated to be a positive value (+) compared with the vanadium electrolyte with an oxidation value of 3.50. This confirms that the charging energy is higher than that of the vanadium electrolyte with an oxidation value of 3.50.

[0134] As described above, according to the vanadium electrolyte of the present invention, although the concentration deviation phenomenon of the positive electrode electrolyte and the negative electrode electrolyte occurs when charging / discharging more than hundreds of times, compared with the 3.50-valent electrolyte generally used in the past, the problem of reduced charging energy is solved, and the effect of increased charging energy is shown. This means that the vanadium electrolyte of the present invention can significantly improve the energy density, thereby having the advantages of being able to improve the life and efficiency of secondary batteries of aqueous electrolytes using vanadium electrolytes, and being able to solve the limitations of space constraints.

[0135] Above, with reference to the accompanying drawings, the embodiments of this specification are described in more detail, but this specification is not necessarily limited to these embodiments, and various modifications can be made without departing from the technical ideas of this specification. Therefore, the embodiments disclosed in this specification are not intended to limit the technical ideas of this specification, but to illustrate, and the scope of the technical ideas of this specification is not limited according to these embodiments. Therefore, the above-mentioned embodiments should be understood in all aspects as illustrative, not limiting. The scope of protection of this specification should be interpreted by the claims, and all technical ideas within the equivalent scope should be interpreted as included in the scope of rights of this specification.

Claims

1. A vanadium ion battery, wherein: The vanadium ion battery comprises more than one vanadium ion battery unit. The vanadium ion battery unit comprises: Positive electrode current collector; A negative electrode current collector, arranged separately from the positive electrode current collector; A separator, disposed between the positive electrode current collector and the negative electrode current collector; a positive electrode electrolyte container formed between the positive electrode current collector and the separator; and a negative electrode electrolyte container formed between the negative electrode current collector and the separator; supplying an electrolyte containing vanadium ions as a positive electrode electrolyte to the positive electrode electrolyte container, and supplying an electrolyte containing vanadium ions as a negative electrode electrolyte to the negative electrode electrolyte container; The electrolyte containing vanadium ions contains vanadium ions with an oxidation value exceeding 3.50 and less than 4.00 and an acidic solution.

2. The vanadium ion battery according to claim 1, wherein: The oxidation number of the electrolyte solution containing vanadium ions is greater than 3.50 and less than 3.

80.

3. The vanadium ion battery according to claim 1, wherein: The vanadium ions of the electrolyte containing vanadium ions are provided by vanadium oxide.

4. The vanadium ion battery according to claim 3, wherein: The vanadium oxide includes one or more of V2O5, VOSO4, V2O3, NH4VO3 and V2O4.

5. The vanadium ion battery according to claim 1, wherein: The acidic solution includes one or more of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid.

6. The vanadium ion battery according to claim 1, wherein: The vanadium ion battery unit further includes a migration portion communicating with the positive electrode electrolyte container and the negative electrode electrolyte container.

7. The vanadium ion battery according to claim 1, wherein: The positive electrode current collector includes a positive electrode metal current collector and a positive electrode carbon current collector. The negative electrode current collector includes a negative electrode metal current collector and a negative electrode carbon current collector.

8. The vanadium ion battery according to claim 1, wherein: The vanadium ion battery unit also includes: a positive solid electrode, disposed in the positive electrolyte container and impregnated with the positive electrolyte; and The negative electrode solid electrode is disposed in the negative electrode electrolyte container and is impregnated with the negative electrode electrolyte.

9. The vanadium ion battery according to claim 1, wherein: The membrane is a hydrocarbon-based membrane containing a hydrocarbon-based polymer.

10. The vanadium ion battery according to claim 9, wherein: The hydrocarbon-based membrane is a membrane formed of the hydrocarbon-based polymer, or a membrane formed by coating the hydrocarbon-based polymer on one or both surfaces of a substrate.

11. The vanadium ion battery according to claim 9, wherein: The hydrocarbon-based polymer is a cation-conductive hydrocarbon-based polymer.

12. The vanadium ion battery according to claim 9, wherein: The hydrocarbon-based polymer includes any one or more of a polyimide-based polymer, a polyetheretherketone-based polymer, a polyethersulfone-based polymer, and a polybenzimidazole-based polymer.

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