Electrolyte comprising vanadium ions and vanadium-ion battery comprising same

Abstract

The present invention relates to an electrolyte comprising vanadium ions and a vanadium-ion battery comprising same and, more specifically, to an electrolyte comprising vanadium ions and a vanadium-ion battery comprising same, wherein the electrolyte has a controlled oxidation number of vanadium ions to mitigate a reduction in charging energy (capacity) caused by concentration deviations in an electrolyte comprising vanadium ions at a positive electrode and a negative electrode during charging and discharging of the vanadium-ion battery employing the electrolyte comprising vanadium ions.

Description

Electrolyte containing vanadium ions and vanadium ion battery containing the same

[0001] The present invention relates to an electrolyte containing vanadium ions and a vanadium ion battery containing the same, and more particularly, to an electrolyte containing vanadium ions in which the oxidation number of the vanadium ions is controlled, and a vanadium ion battery containing the same, so as to improve the phenomenon of reduction in charging energy (capacity) due to the concentration difference phenomenon of the electrolyte containing vanadium ions of the positive and negative electrodes during charging and discharging of a vanadium ion battery using an electrolyte containing vanadium ions.

[0002] Redox Flow Battery (RFB), a type of oxidation-reduction secondary battery, is an electrochemical storage device that stores electrical energy as chemical energy of the electrolyte by charging and discharging it through oxidation and reduction of the active material in the electrolyte, unlike conventional secondary batteries.

[0003] The electrolyte of a redox secondary battery uses a substance having a redox couple. The electrolyte of the early redox secondary battery used redox couples of different substances for the positive and negative electrodes. However, there may be a problem in that the capacity of the battery is reduced due to a phenomenon in which different substances that are ionized during charging and discharging cross over each other through the separator. As an example, the crossover phenomenon may vary in the degree and speed of movement of vanadium ions depending on the type of separator, which may affect the phenomenon of vanadium ion concentration deviation.

[0004] Accordingly, the use of vanadium in both the positive and negative electrodes was proposed as a method to alleviate the ion crossover phenomenon, and since the electrolyte containing vanadium ions is an aqueous electrolyte, it has been used until recently due to its advantages in that it not only has high safety against explosions when applied to secondary batteries, but also increases the lifespan of the batteries.

[0005] Electrolyte containing vanadium ions that use vanadium ions as an active material has the longest lifespan among oxidation-reduction secondary batteries and is advantageous in terms of large capacity. In addition, the electrolyte can be separated and reused through the electrochemical reaction of charging and discharging the secondary battery, which is advantageous in terms of cost.

[0006] The electrolyte containing vanadium ions used in the positive and negative electrodes requires a vanadium compound having an oxidation state of 4+ for the positive electrode and 3+ for the negative electrode, respectively, based on a fully discharged state, and a vanadium compound having an oxidation state of 5+ for the positive electrode and 2+ for the negative electrode is required, based on a fully charged state. The charge and discharge reaction occurs as the oxidation state of the vanadium active material changes, and in order for the electrochemical reversible reaction to occur, it is important to manufacture the positive and negative electrolytes by matching the oxidation states of the vanadium ions.

[0007] The anode and cathode are each anode oxidation-reduction couple (V 4+ / V 5+ ) and cathode oxidation-reduction couple (V 2+ / V 3+ ) is supplied with a dissolved electrolyte solution (electrolyte), which causes the following half-reactions.

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

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

[0010] Generally, as an electrolyte containing vanadium ions, an electrolyte with a vanadium oxidation number of 3.50 (3.5+) that can be commonly used for the electrolyte supplied to the cathode and the electrolyte supplied to the anode has been used.

[0011] However, when using an electrolyte with a vanadium oxidation number of 3.50 as in the past, it was discovered that as charging and discharging were repeated, the concentration of vanadium ions in the positive and negative electrodes varied, which became more severe and resulted in problems such as a decrease in charging energy (capacity).

[0012] Specifically, when charging a redox secondary battery using an electrolyte containing vanadium ions, a concentration difference phenomenon occurs in which the concentration of vanadium ions in the negative electrode decreases and the concentration of vanadium ions in the positive electrode increases. Accordingly, the charging energy decreases, the energy density also decreases, and as a result, the lifespan and efficiency of the redox secondary battery may decrease, resulting in a decline in performance.

[0013] The purpose of the present invention is to provide an electrolyte containing vanadium ions with controlled oxidation numbers so as to alleviate the problem of reduced performance, particularly charging energy (capacity), of a redox secondary battery.

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

[0015] The objects of the present invention are not limited to the purposes mentioned above, and other purposes not mentioned will be clearly understood by those skilled in the art from the description below.

[0016] A vanadium ion battery (VIB) according to one aspect of the present invention may include one or more vanadium ion battery unit cells, wherein the vanadium ion battery unit cells may include: a positive electrode current collector; an anode current collector spaced apart 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 receiving portion formed between the positive electrode current collector and the separator; and a negative electrode electrolyte receiving portion formed between the negative electrode current collector and the separator; wherein an electrolyte containing vanadium ions may be supplied as a positive electrode electrolyte and a negative electrode electrolyte to each of the positive electrode electrolyte receiving portion and the negative electrode electrolyte receiving portion, and the electrolyte containing vanadium ions may include vanadium ions having an oxidation number exceeding 3.50 and less than 4.00 and an acidic solution.

[0017] The oxidation number of the vanadium ion in the electrolyte containing the vanadium ion may be greater than 3.50 and less than or equal to 3.80. For example, the oxidation number of the vanadium ion in the positive electrolyte and the negative electrolyte may be greater than or equal to 3.55 and less than or equal to 3.80.

[0018] The vanadium ions of the electrolyte containing the above vanadium ions may be supplied by vanadium oxide.

[0019] The above vanadium oxide may include one or more of V2O5, VOSO4, V2O3, NH4VO3, and V2O4.

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

[0021] The above vanadium ion battery unit cell may further include a transition portion that connects the positive electrode electrolyte receiving portion and the negative electrode electrolyte receiving portion.

[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 above vanadium ion battery unit cell may further include a positive electrode solid electrode disposed in the positive electrolyte receiving portion and impregnated with the positive electrolyte; and a negative electrode solid electrode disposed in the negative electrolyte receiving portion and impregnated with the negative electrolyte.

[0024] The above-mentioned separation membrane may be a hydrocarbon-based separation membrane including a cationic conductive hydrocarbon-based polymer.

[0025] The above hydrocarbon-based separation membrane may be formed from the hydrocarbon-based polymer, or may be formed by coating one or both sides of a substrate with the hydrocarbon-based polymer.

[0026] The above hydrocarbon polymer may include at least one of a polyimide polymer, a polyetheretherketone polymer, a polyethersulfone polymer, and a polybenzimidazole polymer.

[0027] The electrolyte containing vanadium ions of the present invention can be provided in a state in which the oxidation number exceeds 3.50.

[0028] 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 reduction in charging energy (capacity) due to the deviation in the concentration of vanadium ions between the positive and negative electrodes that occurs during charging and discharging of a vanadium ion battery can be improved.

[0029] When the electrolyte containing vanadium ions of the present invention is applied, the energy density of a vanadium ion battery can be significantly increased, and further, it can be advantageous in improving the efficiency and lifespan of the vanadium ion battery. This is because a battery with a high energy density has a relatively low state of charge (SoC) even when charging the same amount of energy, so the potential difference between the positive and negative electrodes becomes small, and thus the possibility of irreversible reactions such as hydrogen generation is reduced, and a battery with a high energy density uses a smaller depth of discharge (DoD) even when discharging the same amount of energy, so the long-term lifespan of the battery is extended, and there is an advantage of being able to use a more efficient section.

[0030] The vanadium ion battery of the present invention is designed with a structure excluding the electrolyte storage tank and the fluid pump for electrolyte flow of a conventional redox flow battery (RFB), and therefore has an advantage in securing space when manufacturing a large-scale energy storage system (ESS).

[0031] Since the electrolyte containing vanadium ions of the present invention has a higher energy density than when using a conventional 3.50-valent vanadium electrolyte, there is an advantage in that the size of an aqueous secondary battery using the electrolyte can be further reduced.

[0032] When the electrolyte containing vanadium ions of the present invention is applied, the effect of improving the phenomenon of reduction in charging energy (capacity) in a vanadium ion battery with a sealed structure can be further improved.

[0033] The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

[0034] FIG. 1 is an exploded perspective view of a vanadium ion battery unit cell according to one embodiment of the present invention.

[0035] FIG. 2 is a perspective view of a vanadium ion battery unit cell according to one embodiment of the present invention.

[0036] FIG. 3 is a 3-3 cross-sectional view of the vanadium ion battery unit cell illustrated in FIG. 2.

[0037] FIG. 4 is a perspective view schematically illustrating the structure of a vanadium ion battery in which vanadium ion battery unit cells are stacked according to one embodiment of the present invention.

[0038] Figure 5 shows a titration graph for confirming the oxidation number of an electrolyte containing vanadium ions according to one embodiment of the present invention.

[0039] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0040] In describing this specification, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of this specification, the detailed description is omitted.

[0041] Although terms like "first" and "second" are used herein to describe various components, these components are not limited by these terms. These terms are used merely to distinguish one component from another, and unless otherwise specifically stated, a "first" component may also be a "second" component.

[0042] Throughout this specification, unless otherwise specifically stated, each component may be singular or plural.

[0043] In interpreting the components in this specification, even if there is no separate explicit description, it is interpreted as including the error range.

[0044] In this specification, the phrase "any component is disposed "on (or below)" a component or "on (or below)" a component may mean not only that any component is disposed in contact with the upper surface (or lower surface) of said component, but also that another component may be interposed between said component and any component disposed on (or below) said component.

[0045] When it is described herein that any component is “connected,” “coupled,” or “connected” to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be “interposed” between the components, or that each component may be “connected,” “coupled,” or “connected” through another component.

[0046] In this specification, when the terms "includes," "has," "consists of," "arranges," and "provides" are used for a component, other parts may be added, unless "only" is used. When a component is expressed in the singular, it includes the plural unless otherwise explicitly stated.

[0047] Throughout this specification, when we refer to "A and / or B", this means A, B, or A and B, unless otherwise stated, and when we refer to "C to D", this means C or more and D or less, unless otherwise stated.

[0048] Unless otherwise specified in this specification, any reference to a unit is interpreted as meaning “weight.”

[0049] In this specification, unless otherwise specifically stated, “electrolyte containing vanadium ions” is interpreted to refer to the same thing as “vanadium ion electrolyte,” “electrolyte using (utilizing) vanadium ions,” “electrolyte containing vanadium oxide,” “vanadium electrolyte,” “electrolyte containing vanadium active material,” etc.

[0050] In this specification, the oxidation number of vanadium ions in the vanadium ion electrolyte may be the oxidation number of the electrolyte itself at the time of manufacture or supply, or the average value of the oxidation numbers of the electrolyte supplied to the positive and negative electrodes, and may represent the average value of the oxidation numbers of the positive and negative electrolytes when the secondary battery is operated by charging and discharging.

[0051]

[0052] < Electrolyte containing vanadium ions >

[0053] Hereinafter, an electrolyte containing vanadium ions according to one aspect of the present invention will be described in detail.

[0054]

[0055] Conventionally, a vanadium electrolyte having an oxidation number of 3.50 is used in a redox secondary battery that uses an electrolyte containing vanadium ions. In particular, when the secondary battery is charged and discharged hundreds or thousands of times or more, the phenomenon of deviation in the concentration of vanadium ions in the vanadium electrolyte injected into the positive and negative electrodes becomes increasingly severe, and the charging energy (capacity) of the secondary battery decreases, resulting in a decline in performance. The inventors of the present invention have experimentally confirmed that when a vanadium electrolyte having an oxidation number exceeding 3.50 is used instead of the conventional vanadium electrolyte having an oxidation number of 3.50, the phenomenon of decreasing charging energy (capacity), which is a problem when charging and discharging a redox secondary battery is repeated multiple times, can be resolved despite the occurrence of deviation in the concentration of vanadium ions, and have devised the present invention.

[0056] Thus, the electrolyte containing vanadium ions of the present invention comprises vanadium ions and an acidic solution, and is characterized in that the oxidation number of the vanadium ions is greater than 3.50, for example, greater than 3.55, and at this time, it can exhibit the effect of solving the problem of reduction in charging energy. In particular, the effect increases further as the number of charge / discharge cycles increases.

[0057] Specifically, the electrolyte in which the oxidation number of the vanadium ion exceeds 3.50 tends to have a somewhat lower charging energy after several charge / discharge cycles compared to the conventional electrolyte in which the oxidation number of the vanadium ion is 3.50. However, it was experimentally confirmed that the charging energy actually increases as the charging / discharging cycles are repeated tens or hundreds of times. Considering that redox secondary batteries are generally operated by charging / discharging hundreds or thousands of times or more, the experimental results of the present invention can be interpreted as very meaningful results. In particular, since the electrolyte including the vanadium ion of the present invention can have improved energy density, the size of a redox secondary battery using an aqueous electrolyte like the present invention can be significantly reduced, and the efficiency and lifespan of the redox secondary battery can be improved.

[0058] Meanwhile, when the oxidation number of the vanadium ion in the electrolyte becomes lower than 3.50, not only does the charging energy decrease after several charging and discharging cycles, but the charging energy also decreases further after tens or hundreds of charging and discharging cycles.

[0059] On the other hand, if the oxidation number of the vanadium ion increases too much, the effect of mitigating the decrease in the charging energy decrease is lowered again. For example, the oxidation number of the vanadium ion may be less than 4.00, for example, the oxidation number of the vanadium ion may be less than 3.70, for example, the oxidation number of the vanadium ion may be less than 3.65, but this may vary depending on the path along which the vanadium ion moves.

[0060] According to one embodiment of the present invention, the vanadium ion of the vanadium electrolyte of the present invention may be supplied by vanadium oxide, and may include, for example, at least one selected from the group consisting of V2O5, VOSO4, V2O3, NH4VO3, and V2O4, but is not necessarily limited thereto, and may be selected according to electrolyte production conditions, production target amount, etc.

[0061] According to one embodiment of the present invention, the form in which the vanadium oxide is supplied is not particularly limited, but may be, for example, in powder form in terms of process efficiency.

[0062] According to one embodiment of the present invention, the acidic solution may include at least one 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.

[0063] The concentration of the acidic solution may be, for example, 0.1 M to 10 M, for example, 1 M to 8 M, for example, 2 M to 5 M, but is not necessarily limited thereto, and may be appropriately adjusted depending on the type of acidic solution selected, etc.

[0064] The concentration of vanadium ions in the electrolyte containing the above vanadium may be 1.5 M to 3.0 M.

[0065]

[0066] Vanadium ion battery

[0067] Hereinafter, a vanadium ion battery according to another aspect of the present invention will be described in detail.

[0068] As the overall size of a redox flow battery using vanadium electrolyte has become very large due to the electrolyte storage tank and fluid pump for electrolyte flow of a conventional redox flow battery (RFB), there have been limitations due to space constraints and design difficulty. Therefore, in the present invention, a Vanadium Ion Battery (VIB), which is a sealed redox secondary battery, is used, excluding the electrolyte tank and fluid pump. Specifically, the unit cell including a positive electrode collector; an anode collector disposed spaced apart from the positive electrode collector; and a separator disposed between the positive electrode collector and the negative electrode collector; is designed by stacking one or more of them so that the internal structure of the battery can be circulated without a pump. As a result, compared to a conventional redox flow battery, the power density can be improved by up to 2-50 times, and the stability of energy output can be increased.

[0069] A vanadium ion battery according to one embodiment of the present invention may include one or two or more vanadium ion battery unit cells, for example, three or more, and for example, after being stacked in this manner, the stacked unit cells may be additionally electrically connected in parallel.

[0070]

[0071] A vanadium ion battery unit cell is described in detail with reference to FIGS. 1 to 3.

[0072] A vanadium ion battery unit cell (100) according to the present invention includes: a positive electrode current collector (130a); a negative electrode current collector (130b) disposed spaced apart from the positive electrode current collector; a separator (120) disposed between the positive electrode current collector (130a) and the negative electrode current collector (130b); a positive electrode electrolyte receiving portion (111a) formed between the positive electrode current collector (130a) and the separator (120); and a negative electrode electrolyte receiving portion (111b) formed between the negative electrode current collector (130b) and the separator (120).

[0073] The positive electrode current collector (130a) and the negative electrode current collector (130b) of the vanadium ion battery unit cell (100) can be manufactured by stacking metal current collectors (131a, 131b) and carbon current collectors (132a, 132b), respectively. The metal current collectors (131a, 131b) may be formed of a metal having high electrical conductivity (e.g., copper or aluminum) and may be connected to a busbar for electrically connecting each unit cell. The carbon current collectors (132a, 132b) may be formed of a material such as graphite, carbon, carbon plastic, etc. and may have high electrical conductivity and high acid resistance. The metal current collectors (131a, 131b) and carbon current collectors (132a, 132b) may be formed in a rectangular plate shape.

[0074]

[0075] A vanadium ion battery unit cell (100) may include a support (110) for providing a space for a positive electrolyte receiving portion (111a) and a negative electrolyte receiving portion (111b) while arranging a separator (120) between the positive electrode current collector (130a) and the negative electrode current collector (130b). The support (110) may be attached to the carbon current collectors of the positive electrode current collector (130a) and the negative electrode current collector (130b), and due to this structure, a sealed structure may be formed, thereby ensuring the airtightness required for a vanadium ion battery.

[0076]

[0077] An electrolyte containing vanadium ions may be supplied as a positive electrolyte and a negative electrolyte to each of the positive electrolyte receiving portion (111a) and the negative electrolyte receiving portion (111b). The supplied electrolyte is an electrolyte containing vanadium ions according to one embodiment of the present invention described above, and may include vanadium ions having an oxidation number greater than 3.50 and less than 4.00 and an acidic solution, and according to one embodiment, may include vanadium ions having an oxidation number greater than 3.50 and less than 3.80. For example, the electrolyte may include vanadium ions having a vanadium ion oxidation number of 3.55 or more and 3.80 or less.

[0078]

[0079] According to one embodiment of the present invention, a vanadium ion battery unit cell (100) may include a transition portion (112) that connects the positive electrolyte receiving portion and the negative electrolyte receiving portion. The transition portion (112) may be formed on a support (110).

[0080] The above transition portion (112) is intended to resolve the imbalance caused by the phenomenon of ionized substances (vanadium ions, ionized H2O, ions of acidic aqueous solution, etc.) crossing each other through the separator (120) during charging and discharging of the secondary battery.

[0081] More specifically, when charging and discharging are repeated, a phenomenon may occur in which the volume of the electrolyte contained in the positive electrolyte containing portion (111a) and the negative electrolyte containing portion (111b) changes. When charging a vanadium ion battery, some ions (ionized H2O, vanadium ions, SO4) pass through the separator. 2- ) can move. In addition, the volume of the negative electrolyte may increase due to the strong attraction of the divalent vanadium ions present in the negative electrolyte receiving portion to the ionized H2O. As a result, the concentration of vanadium ions in the negative electrode may decrease, and the concentration of vanadium ions in the positive electrode may increase.

[0082] In this way, as charging and discharging are repeated, an imbalance occurs in which the volumes of the negative and positive electrolytes change. Therefore, in the present invention, the electrolyte can move from a relatively larger electrolyte receiving portion to a smaller electrolyte receiving portion through the transition portion (112), thereby resolving the imbalance in the electrolyte volumes.

[0083] Meanwhile, when discharging a redox secondary battery using an electrolyte containing vanadium ions, water, vanadium ions, and anions contained in the acidic solution of the electrolyte (for example, HSO4 in the case of sulfuric acid) pass through the transition portion (112). - ) can move from the cathode electrolyte to the anode electrolyte, which may further aggravate the phenomenon of the vanadium concentration in the cathode electrolyte decreasing and the vanadium concentration in the anode electrolyte increasing.

[0084] In this way, in the vanadium ion battery (VIB) of the present invention, the decrease in energy density due to the vanadium concentration imbalance phenomenon of the positive and negative electrolytes that occurs during charge and discharge can be resolved by applying an electrolyte containing vanadium ions according to one aspect of the present invention.

[0085] Furthermore, as the charging and discharging of the vanadium ion battery is repeated, the charging energy is improved compared to when the conventional 3.50 valence vanadium ion electrolyte is used, which can result in increasing the efficiency and lifespan of the vanadium ion battery and reducing the volume of the vanadium ion battery.

[0086]

[0087] Meanwhile, according to one embodiment of the present invention, the vanadium ion battery unit cell (100) may further include a positive electrode solid electrode (150a) disposed in the positive electrolyte receiving portion (111a) and impregnated with the positive electrolyte; and a negative electrode solid electrode (150b) disposed in the negative electrolyte receiving portion (111b) and impregnated with the negative electrolyte.

[0088] The positive solid electrode (150a) and the negative solid electrode (150b) may be respectively immersed in the positive electrolyte and the negative electrolyte and placed in the positive electrolyte receiving portion (111a) and the negative electrolyte receiving portion (111b). The positive solid electrode (150a) and the negative solid electrode (150b) may include carbon-based materials such as carbon or graphite felt, carbon fiber, carbon black, graphite powder, or graphene. The positive solid electrode (150a) may be in close contact with the positive current collector (130a) and the separator (120), and the negative solid electrode (150b) may be in close contact with the negative current collector (130b) and the separator (120).

[0089] The phenomenon of vanadium ions of vanadium electrolyte crossing each other through the vanadium ion battery separator may vary in the degree and speed of movement of vanadium ions depending on the type of separator, which may affect the vanadium ion concentration deviation phenomenon. Therefore, the separator (120) of the vanadium ion battery unit cell (100) of the present invention may include a hydrocarbon-based separator including a cation-conductive hydrocarbon-based polymer. Nafion, which has been commonly used ® Since it is formed of a fluorine-based cationic conductive polymer, it has the disadvantage of being vulnerable to contamination of secondary batteries as it can leak halogen substances. In addition, in aqueous batteries, protons (H) in the electrolyte +) may generate pressure inside the cell due to microfluidic movement and side reactions (evolution of gases such as H2 and CO2) that commonly occur in aqueous batteries. Therefore, in a vanadium ion battery (VIB) with a sealed structure, it is necessary to have excellent mechanical strength to withstand such pressure, high stability to prevent irreversible and side reactions, and further secure excellent acid resistance even when immersed in an acidic electrolyte for a long time. Therefore, it is desirable to use a hydrocarbon-based separator.

[0090] The hydrocarbon-based separation 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 membrane may be coated by impregnating one or both sides of a porous substrate with a solution of the hydrocarbon-based polymer dissolved in a solvent and then drying the solution. The hydrocarbon-based polymer is a polymer containing a carbon and hydrogen skeleton, and the carbon and hydrogen skeleton may be aliphatic, alicyclic, aromatic, or a combination thereof, and may further contain heteroatoms such as oxygen, sulfur, nitrogen, silicon, boron, and selenium. Non-limiting examples of the carbon and hydrogen skeleton include an alkyl group, an alkenyl group, an alkynyl group, a heteroalkyl group, an aryl group, a heteroaryl group, an aralkyl group, a heteroaralkyl group, an amide group, a sulfonyl group, an ether group, a ketone group, an ester group, and a combination thereof. The above hydrocarbon polymer may be substituted with a substituent such as a cyano group, a nitro group, an amine group, a hydroxyl group, an alkyl group, an alkoxy group, a ketone group, a carboxyl group, an ether group, an ester group, a sulfonic acid group, a sulfonyl group, a silyl group, etc.

[0091] The porous substrate may be selected to exhibit high tensile strength (e.g., 100 MPa or more) even with a thin thickness, and exhibit excellent hydrocarbon polymer impregnation properties and post-dry coating properties. For example, a porous substrate made of polypropylene (PP) or polyethylene (PE) may be selected, but is not necessarily limited thereto.

[0092] The above hydrocarbon polymer may include any one of a polyimide polymer, a polyetheretherketone polymer, a polyethersulfone polymer, and a polybenzimidazole polymer.

[0093]

[0094] Referring to FIG. 4, the vanadium ion battery (1000) of the present invention can be manufactured by stacking a plurality of vanadium ion battery unit cells (100). The plurality of vanadium ion battery unit cells (100) can be electrically connected by a busbar (200). Some of the metal current collectors (131a, 131b) of the plurality of vanadium ion battery unit cells (100) can be electrically connected to the busbar (200) by a protrusion (100c).

[0095] A pair of endplates (300) are arranged at the top and bottom of a plurality of vanadium ion battery unit cells (100). The endplates (300) are made of a relatively strong insulating material or an insulated metal material.

[0096] The bus bar (200) transmits electricity generated in a plurality of unit cells (100) to the outside during discharge and transmits external electricity to the plurality of unit cells (100) during charging. The bus bar (200) can connect a plurality of unit cells (100) in parallel or series. The bus bar (200) can be arranged to cover one side of the plurality of unit cells (100) and one side of a pair of end plates (300).

[0097] Hereinafter, the present invention will be described in more detail by describing manufacturing examples and experimental examples. However, these are only examples of the present invention, and the present invention is not limited thereto.

[0098]

[0099] Manufacturing Example 1: Manufacturing of an electrolyte containing vanadium ions

[0100] A stirrer was installed in a heating mantle heated to approximately 80°C, and then 3rd distilled water (DI water; DW) manufactured with a 3rd ultrapure water device, 98% sulfuric acid (H2SO4), and 99.5% oxalic acid as a reducing agent were first introduced, and then V2O5 powder was added in small amounts.

[0101] At this time, to prepare 1 L of vanadium electrolyte, 236 ml of 98% H2SO4, 108 g of 99.5% oxalic acid, and 780 ml of DW were mixed, and then 154 g of V2O5 powder was added to prepare a 1.7 M vanadium ion electrolyte. Then, heating and stirring at approximately 80°C were performed for approximately 12 hours.

[0102] Vanadium was sufficiently dissolved in sulfuric acid to prepare a vanadium electrolyte having an oxidation number of 4. Then, the vanadium electrolyte having an oxidation number of 4 was injected into a VRFB cell (manufactured by Standard Energy) for performing electrochemical reduction, and then reduced at the cathode to prepare vanadium ion electrolytes having oxidation numbers of 3.45, 3.50, 3.55, 3.60, 3.65, 3.70, and 3.80, respectively.

[0103] At this time, the oxidation number of the vanadium ion electrolyte prepared above can be calculated according to the following equation 1 by a titration method using an oxidizing agent.

[0104] <Formula 1> Average oxidation number of vanadium ion electrolyte = 5 - {V b / (V b - V a )}

[0105] In the above equation 1, V a V means the amount (ml) of oxidizing agent consumed when the oxidation number of vanadium electrolyte is oxidized from more than 3.00 to 4.00. bIt means the amount (ml) of oxidizing agent consumed when the oxidation number of vanadium electrolyte is oxidized from more than 3.00 to 5.00.

[0106] As shown in Fig. 5, when an oxidizing agent is added dropwise to a vanadium electrolyte having an oxidation number of 3.00, the relative potential value (V) to the reference electrode, Ag / AgCl, is measured, and a vanadium electrolyte titration graph is plotted. Then, when a first derivative graph is plotted, there are two inflection points indicated by peaks. The inflection points here represent equivalence points, which are points where the oxidation number of the vanadium electrolyte changes. Based on the inflection points, V is the amount (ml) of the oxidizing agent consumed when the oxidation number of the vanadium electrolyte is oxidized from more than 3.00 to 4.00. a And V is the amount (ml) of oxidizing agent consumed when the oxidation number of vanadium electrolyte is oxidized from more than 3.00 to 5.00. b You can check it, (V b - V a ) represents the amount of oxidant consumed (ml). In Fig. 5, Potential (V vs Ag / AgCl) represents the relative potential value (V) for the reference electrode, Ag / AgCl, and △V / △mL represents the differential of the change in potential value (△V) with respect to the volume (△mL) of the consumed oxidant.

[0107] In the present invention, 0.02M KMnO4 was used as the oxidizing agent, and as confirmed in Fig. 5, V a is 1.6 (ml), V b Since it was 4.8(ml), if calculated according to the above equation 2, it is calculated as 5 - {4.8 / (4.8 - 1.6)} = 3.5, so it can be seen that the oxidation number is 3.5.

[0108] According to this titration method, the oxidation number value of each vanadium electrolyte prepared above can be measured.

[0109]

[0110] Manufacturing Example 2: Manufacturing of a vanadium ion battery

[0111] Two current collectors were manufactured by stacking a carbon current collector (graphite composite, thickness: 0.2 mm) and a metal current collector (aluminum foil, thickness: 0.2 mm), and were used as a positive current collector and a negative current collector, respectively.

[0112] A cation exchange membrane (thickness: 20 μm, Standard Energy Co.) manufactured by coating polyethylene (PE) with m-PBI (poly[2,2-(m-phenylene)-5,5bibenzimidazole) was used as a separation membrane (hereinafter referred to as 'PBI separation membrane').

[0113] After preparing a hollow square support, a positive electrode current collector and a negative electrode current collector were placed on both sides of the support, and the PBI separator was placed in the center of the support to form a positive electrode electrolyte receiving portion and a negative electrode electrolyte receiving portion while separating the positive electrode current collector and the negative electrode current collector. A transition portion connecting the positive electrode electrolyte receiving portion and the negative electrode electrolyte receiving portion was formed on the support, thereby manufacturing a vanadium ion battery unit cell.

[0114]

[0115] Experimental example: Charge and discharge experiment of vanadium ion battery

[0116] In order to confirm the charging energy performance during charging and discharging according to each oxidation state of the vanadium ion electrolyte prepared in Manufacturing Example 1, the vanadium ion electrolyte with an oxidation state of 3.50 prepared in Manufacturing Example 1 was added to the positive and negative electrodes of the vanadium ion battery prepared in Manufacturing Example 2.

[0117] As for the charge / discharge operation conditions, the battery was charged with a constant current of 0.5 C until the voltage reached 1.70 V, and discharged with a constant current of 0.5 C until the voltage reached 1.10 V, which is the same as the charge.

[0118] Charging and discharging were performed up to 500 times (cycles) under the above charging and discharging conditions, and the charging energy (wh) was calculated for each of the 5, 100, 200, 300, 400, and 500 cycles. The charging energy is a value calculated by multiplying the charging voltage measured at each measurement time (sampling time) while the battery was being charged by the charging current (0.5 C).

[0119] Then, for vanadium ion electrolytes with oxidation numbers of 3.45, 3.50, 3.55, 3.60, 3.65, 3.70, and 3.80, charging and discharging were performed up to 500 cycles, and the charging energy was measured at 5, 100, 200, 300, 400, and 500 cycles, respectively.

[0120] Based on the vanadium ion electrolyte having an oxidation number of 3.50, the increase / decrease rate (percentage; %) of the charging energy of vanadium ion electrolytes having oxidation numbers of 3.45, 3.50, 3.55, 3.60, 3.65, 3.70, and 3.80 was calculated according to the following Equation 2, and is shown in Table 1 below.

[0121] <Equation 2> Increase / decrease rate of charging energy: { (E x - E 3.5 ) / E 3.5} × 100 (%)

[0122] In the above equation 2, E 3.5 is the charging energy of the vanadium ion electrolyte with oxidation number 3.50, E x refers to the charging energy of vanadium ion electrolyte with oxidation number other than 3.50.

[0123] [Table 1]

[0124]

[0125] As can be seen in Table 1 above, the increase / decrease rate of charge energy of the vanadium electrolyte exceeding the oxidation number 3.50 after 200 charge / discharge cycles was calculated as a positive value (+) compared to the vanadium electrolyte with the oxidation number 3.50, which confirmed that the charge energy was higher than that of the vanadium electrolyte with the oxidation number 3.50.

[0126] In this way, the vanadium electrolyte according to the present invention, despite the phenomenon of concentration deviation of the positive and negative electrolytes occurring during hundreds of charge and discharge cycles, solved the problem of reduced charging energy and rather showed the effect of increased charging energy compared to the conventional 3.50-valent electrolyte, which is generally used. This means that the vanadium electrolyte of the present invention can have significantly improved energy density, and thus can increase the lifespan and efficiency of a secondary battery of an aqueous electrolyte using the vanadium electrolyte, and can also have the advantage of overcoming limitations due to space constraints.

[0127]

[0128] Although the embodiments of the present specification have been described in more detail with reference to the attached drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be implemented without departing from the technical spirit of the present specification. Therefore, the embodiments disclosed in this specification are not intended to limit the technical spirit of the present specification, but to explain, and the scope of the technical spirit of the present specification is not limited by these embodiments. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of protection of this specification should be interpreted by the claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of rights of this specification.

[0129]

[0130] [Explanation of symbols]

[0131] 130a: Positive current collector

[0132] 130b: Negative current collector

[0133] 131a: Anode metal current collector

[0134] 131b: Negative metal current collector

[0135] 132a: Anode carbon current collector

[0136] 132b: Negative carbon current collector

[0137] 110: Support

[0138] 111a: Positive electrolyte receiving compartment

[0139] 111b: Cathode electrolyte receiving compartment

[0140] 112: Cheon Ibu

[0141] 120: Membrane

[0142] 150a: Positive solid electrode

[0143] 150b: Cathode solid electrode

[0144] 100: Vanadium ion battery unit cell

[0145] 100c: Metal current collector

[0146] 200: Busbar

[0147] 300: Endplate

[0148] 1000: Vanadium ion battery

Claims

1. As a vanadium ion battery (VIB), The above vanadium ion battery comprises at least one vanadium ion battery unit cell, The above vanadium ion battery unit cell is, positive current collector; A negative electrode current collector disposed spaced apart 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 receiving portion formed between the positive electrode current collector and the separator; and Including a negative electrode electrolyte receiving portion formed between the negative electrode current collector and the separator; An electrolyte containing vanadium ions is supplied as an anode electrolyte and a cathode electrolyte to each of the anode electrolyte receiving portion and the cathode electrolyte receiving portion, The electrolyte containing the above vanadium ion comprises a vanadium ion having an oxidation number exceeding 3.50 and less than 4.00 and an acidic solution. Vanadium ion battery.

2. In paragraph 1, The oxidation number of the vanadium ion in the electrolyte containing the above vanadium ion is 3.55 or more and 3.80 or less. Vanadium ion battery.

3. In paragraph 1, The vanadium ions of the electrolyte containing the above vanadium ions are supplied by vanadium oxide. Vanadium ion battery.

4. In paragraph 3, The above vanadium oxide comprises at least one of V2O5, VOSO4, V2O3, NH4VO3 and V2O4. Vanadium ion battery.

5. In paragraph 1, The above acid solution contains one or more of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid. Vanadium ion battery.

6. In paragraph 1, The above vanadium ion battery unit cell further includes a transition portion that connects the positive electrolyte receiving portion and the negative electrolyte receiving portion. Vanadium ion battery.

7. In paragraph 1, The above positive electrode current collector includes a positive electrode metal current collector and a positive electrode carbon current collector, The above negative electrode current collector includes a negative electrode metal current collector and a negative electrode carbon current collector. Vanadium ion battery.

8. In paragraph 1, The above vanadium ion battery unit cell is, A positive electrode solid electrode disposed in the positive electrode electrolyte receiving portion and impregnated with the positive electrode electrolyte; and Further comprising a cathode solid electrode disposed in the cathode electrolyte receiving portion and impregnated with the cathode electrolyte. Vanadium ion battery.

9. In paragraph 1, The above separation membrane is a hydrocarbon separation membrane containing a hydrocarbon polymer. Vanadium ion battery.

10. In paragraph 9, The above hydrocarbon-based separation membrane is formed by the hydrocarbon-based polymer or by coating the hydrocarbon-based polymer on one or both sides of a substrate. Vanadium ion battery.

11. In paragraph 9, The above hydrocarbon polymer is a cationic conductive hydrocarbon polymer. Vanadium ion battery.

12. In paragraph 9, The above hydrocarbon polymer includes at least one of a polyimide polymer, a polyetheretherketone polymer, a polyethersulfone polymer, and a polybenzimidazole polymer. Vanadium ion battery.

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