Vanadium electrolyte, and secondary battery comprising same

Abstract

The present invention relates to a vanadium electrolyte and to a secondary battery comprising same and, more particularly, to a vanadium electrolyte having a controlled concentration of an element causing a hydrogen evolution reaction (HER) occurring during charging and discharging of a secondary battery, and to a secondary battery comprising the vanadium electrolyte.

Description

Vanadium electrolyte and secondary battery containing the same

[0001] The present invention relates to a vanadium electrolyte and a secondary battery containing the same, and more particularly, to a vanadium electrolyte having a controlled concentration of an element causing a hydrogen evolution reaction (HER) that occurs during charging and discharging of the secondary battery, and a secondary battery containing the vanadium electrolyte.

[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] Meanwhile, 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 ionized substances cross over each other through the separator during charging and discharging, which reduces the capacity of the battery.

[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 ('vanadium electrolyte') 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] Vanadium electrolyte using vanadium ions as the active material has the longest lifespan when applied to redox 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, which is advantageous in terms of cost.

[0006] The vanadium electrolyte 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. In addition, 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. Charge and discharge reactions occur as the oxidation state of the vanadium active material changes.

[0007] The anode and cathode are each the oxidation-reduction couple of the anode (V 4+ / V 5+ ) and the oxidation-reduction couple of the cathode (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] Vanadium electrolyte, which can be commonly used in the electrolyte supplied to the cathode and the electrolyte supplied to the anode, has an oxidation number of 3.5 (V). 3.5+ ) has been using an electrolyte.

[0011] Meanwhile, the hydrogen evolution reaction (HER) inevitably occurs at the cathode of a secondary battery using a vanadium electrolyte, producing hydrogen (H2) gas. The hydrogen gas produced in this way generates V 2+ / V 3+The problem arises that electrons involved in the oxidation and reduction reactions of the electrolyte are used, which interferes with the electrode reaction. In addition, as the pressure of the electrolyte and the secondary battery containing it increases due to hydrogen gas, a considerable amount of effort and cost is required to control safety issues such as a decrease in durability against high pressure or explosion due to pressure increase, and there is also a limit to the usable voltage range. If there is a limit to the usable voltage range due to the generation of hydrogen gas, the energy capacity that can be stored per volume of electrolyte decreases, which causes problems of reduced efficiency such as increased cost of the secondary battery. Therefore, it is necessary to develop a method to suppress the hydrogen generation reaction that is a problem during charging and discharging of a secondary battery in a vanadium electrolyte.

[0012] In addition, compared to conventional vanadium redox flow batteries (VRFB), vanadium ion batteries (VIB) with a sealed structure are more vulnerable to hydrogen gas generation due to the problem of increased pressure within the vanadium ion battery when hydrogen gas is generated, so it is more important to develop a technological solution that can effectively suppress hydrogen generation.

[0013] The purpose of the present invention is to provide a vanadium electrolyte capable of suppressing a hydrogen generation reaction in a secondary battery using a vanadium electrolyte, and a secondary battery including the vanadium electrolyte.

[0014] Another object of the present invention is to improve the efficiency and lifespan of a secondary battery including a vanadium electrolyte capable of suppressing a hydrogen generation reaction, increase the usable voltage range of the secondary battery, and significantly reduce or eliminate the risk of explosion due to hydrogen gas by using a vanadium electrolyte capable of suppressing a hydrogen generation reaction.

[0015] Another object of the present invention is to control the concentration of elemental ions that may cause a decrease in voltage efficiency and / or Coulombic efficiency when applied to a vanadium ion battery.

[0016] 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 entire description of this specification.

[0017] In order to achieve the above task, according to the first aspect of the present invention, a vanadium ion is included, and V 3+ / V 4+ The total concentration of impurity elements with a standard reduction potential value higher than 0.337 V, which is the standard reduction potential value of , is 1.449×10 4 A vanadium electrolyte is provided, wherein the content is less than ppb and the impurity element does not include vanadium (V).

[0018] In one embodiment, V 3+ / V 4+ The standard reduction potential value of 0.337 V or higher and V 4+ / V 5+ The total concentration of impurity elements with standard reduction potentials less than 1 V, which is the standard reduction potential of , is 1.257×10 4 It may be less than ppb.

[0019] In one embodiment, V 4+ / V 5+ The total concentration of impurity elements with a standard reduction potential greater than 1 V, which is the standard reduction potential of , is 2.662 × 10 3 It may be less than ppb.

[0020] In one embodiment, the sum of the concentrations of impurity elements having standard reduction potentials of 0.4 V to 0.6 V is 9.888×10 3 It may be less than ppb.

[0021] In one embodiment, at least one of the following conditions (1) to (3) may be satisfied.

[0022] (1) The concentration of ruthenium (Ru) ions is 1.400 × 10 3 less than ppb

[0023] (2) The concentration of copper (Cu) ions is 1.980 × 10 2 less than ppb

[0024] (3) The concentration of teryllium (Te) ions is 8.290 × 10 3 less than ppb

[0025] In one embodiment, the sum of the concentrations of impurity elements having standard reduction potentials of 0.6 V to 0.8 V is 1.937×10 3 It may be less than ppb.

[0026] In one embodiment, at least one of the following conditions (4) to (7) may be satisfied.

[0027] (4) The concentration of silver (Ag) ions is 2.600 × 10 2 less than ppb

[0028] (5) The concentration of rhodium (Rh) ions is less than 4.500 ppb.

[0029] (6) The concentration of osmium (Os) ions is 1.530 × 10 3 less than ppb

[0030] (7) The concentration of palladium (Pd) ions is 1.429 × 10 2 less than ppb

[0031] In one embodiment, at least one of the following conditions (8) to (10) may be satisfied.

[0032] (8) The concentration of iridium (Ir) ions is 7.470 × 10 2 less than ppb

[0033] (9) The concentration of platinum (Pt) ions is less than 4.500 ppb.

[0034] (10) The concentration of gold (Au) ions is 1.910 × 10 3 less than ppb

[0035] In one embodiment, V 2+ / V3+ The standard reduction potential value of -0.26 V or higher and V 3+ / V 4+ The total concentration of impurity elements with standard reduction potentials lower than 0.337 V, which is the standard reduction potential of , is 4450×10 2 I would be more satisfied with something below ppb.

[0036] In one embodiment, at least one of the following conditions (11) to (12) may be satisfied.

[0037] (11) The concentration of nickel (Ni) ions is 2.080 × 10 5 less than ppb

[0038] (12) The concentration of antimony (Sb) ions is 2.370 × 10 5 less than ppb

[0039] In one embodiment, the vanadium ions may be supplied by a vanadium oxide comprising one or more of V2O5, VOSO4, V2O3, NH4VO3, and V2O4.

[0040] In one embodiment, the vanadium electrolyte may comprise an acidic solution comprising one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

[0041] According to a second aspect of the present invention, a vanadium ion battery unit cell comprises at least one vanadium ion battery unit cell, wherein the vanadium ion battery unit cell comprises:

[0042] positive current collector;

[0043] A negative electrode current collector disposed spaced apart from the positive electrode current collector;

[0044] A separator disposed between the positive electrode current collector and the negative electrode current collector;

[0045] A cathode electrolyte receiving portion formed between the cathode current collector and the separator;

[0046] A negative electrode electrolyte receiving portion formed between the negative electrode current collector and the separator;

[0047] A positive electrode solid electrode disposed in the positive electrode electrolyte receiving portion and impregnated with the positive electrode electrolyte; and

[0048] A cathode solid electrode disposed in the cathode electrolyte receiving portion and impregnated with the cathode electrolyte;

[0049] 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,

[0050] The electrolyte containing the above vanadium ions provides a vanadium ion battery, which is a vanadium electrolyte according to the first aspect of the present invention.

[0051] In one embodiment, the vanadium ion battery unit cell may further include a transition portion that connects the positive electrolyte receiving portion and the negative electrolyte receiving portion.

[0052] In one embodiment, 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.

[0053] The vanadium electrolyte according to the present invention can suppress the hydrogen generation reaction when applied to a secondary battery by controlling the concentration of element ions that cause the hydrogen generation reaction, increase the usable voltage range of the secondary battery, and significantly reduce or eliminate the pressure increase due to hydrogen gas generation and the risk of explosion caused by this.

[0054] In addition, the present invention uses a vanadium electrolyte capable of suppressing hydrogen generation reaction, thereby solving problems related to current consumption due to hydrogen gas and inhibition of oxidation / reduction reactions.

[0055] Furthermore, a secondary battery using the vanadium electrolyte of the present invention can increase the energy capacity that can be stored per volume of electrolyte, and can improve the efficiency and lifespan of the secondary battery.

[0056] In addition, the vanadium electrolyte of the present invention can further improve the efficiency of a vanadium ion battery by controlling the concentration of element ions that may cause a decrease in voltage efficiency and / or coulombic efficiency when applied to a vanadium ion battery to a certain level or less.

[0057] 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.

[0058] FIG. 1 is an exploded perspective view of a vanadium ion battery unit cell according to one embodiment of the present invention.

[0059] FIG. 2 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.

[0060] FIG. 3 is a perspective view of a vanadium ion battery unit cell according to one embodiment of the present invention.

[0061] Figure 4 is a 3-3 cross-sectional view of the vanadium ion battery unit cell illustrated in Figure 3.

[0062] Figure 5 shows the oxidation-reduction couple of the cathode at the standard reduction potential for each element (V 2+ / V 3+ ) to show the selection of elements that can be adsorbed on the cathode surface. NHE in Fig. 5 stands for Normal Hydrogen Electrode.

[0063] Figures 6a and 6b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each ruthenium (Ru) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 1 of the present invention.

[0064] Figures 7a and 7b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each copper (Cu) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 2 of the present invention.

[0065] Figures 8a and 8b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each concentration of teryllium (Te) ions in the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 3 of the present invention.

[0066] Figures 9a and 9b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each silver (Ag) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 4 of the present invention.

[0067] Figures 10a and 10b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each rhodium (Rh) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 5 of the present invention.

[0068] Figures 11a and 11b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each osmium (Os) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 6 of the present invention.

[0069] Figures 12a and 12b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each palladium (Pd) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 7 of the present invention.

[0070] Figures 13a and 13b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each iridium (Ir) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 8 of the present invention.

[0071] Figures 14a and 14b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each platinum (Pt) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 9 of the present invention.

[0072] Figures 15a and 15b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each gold (Au) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 10 of the present invention.

[0073] Figures 16a and 16b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each nickel (Ni) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 11 of the present invention.

[0074] Figures 17a and 17b are graphs plotting the change in pressure (kPa) (vertical axis) against the number of charge / discharge cycles (horizontal axis) at each antimony (Sb) ion concentration of the vanadium electrolyte as the results of the first and second charge / discharge experiments of Experimental Example 12 of the present invention.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] Throughout this specification, unless otherwise specifically stated, each component may be singular or plural.

[0079] In interpreting the components in this specification, even if there is no separate explicit description, it is interpreted to include the range of error.

[0080] 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.

[0081] 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.

[0082] In this specification, when the terms "includes," "contains," "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.

[0083] 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.

[0084] Unless otherwise specified herein, any reference to a unit is interpreted as meaning “weight (wt).”

[0085] In this specification, “vanadium electrolyte” means containing vanadium ions as an active material, unless otherwise specifically stated, and is interpreted as referring to the same subject as “electrolyte containing vanadium ions,” “electrolyte using (utilizing) vanadium ions,” “electrolyte containing vanadium oxide,” “electrolyte containing vanadium active material,” etc.

[0086] In the present invention, the ion of an element is a general term for all ions of valence arising from the same element, and the concentration of any element ion represents the total concentration of all ions of valence arising from the same element.

[0087] In the present invention, the standard reduction potential is a potential value at which a reduction current or oxidation current occurs under a standard state (1 M, 25°C). The standard reduction potential value of each element is a value using a normal hydrogen electrode (NHE), which is a hydrogen electrode using a hydrochloric acid solution with a concentration of 1 N, as a reference electrode.

[0088] In this specification, the concentration of the target element is expressed in units of “ppb” and with four significant figures.

[0089]

[0090] Hereinafter, the present invention will be described in more detail.

[0091]

[0092] The vanadium electrolyte according to the present invention contains vanadium ions, V 3+ / V 4+ The total concentration of impurity elements with a standard reduction potential value higher than 0.337 V, which is the standard reduction potential value of , is 1.449×10 4 Less than ppb, preferably 3.077×10 3It is characterized by being less than ppb. Since the vanadium electrolyte of the present invention contains vanadium ions as an active material, the "impurity element" in the present invention does not contain vanadium (V), and is interpreted as not containing any vanadium in the ionic state, regardless of the valence of the ions.

[0093] The present inventors focused on the mechanism of the hydrogen evolution reaction in order to find elements in the electrolyte that affect the pressure of vanadium. According to the mechanism of the hydrogen evolution reaction, the target elements adsorbed on the cathode are greatly affected by the binding energy with the electrode material, and therefore, 25 elements that are likely to be adsorbed on the cathode surface were selected based on the standard reduction potential of vanadium ions (see Fig. 5). By controlling the concentration (content) of the 25 selected element ions in the vanadium electrolyte, the limit concentration (concentration critical point) of the element ions that does not cause the hydrogen evolution reaction, i.e., can suppress the pressure increase due to hydrogen gas, was experimentally confirmed, thereby leading to the invention of the present invention. The 25 selected elements are Ni, Co, Mo, Sn, Pb, W, Fe, Ge, Sb, Re, Bi, Ru, Cu, Te, Se, Rh, Ag, Os, Pd, Au, Pt, Ir, Cd, In, and Tl.

[0094] In particular, the standard reduction potential value of each of the 25 elements selected above was measured (see Table 1 below), and as a result of conducting a pressure generation experiment by an actual hydrogen evolution reaction for the 25 elements, among the vanadium ion pairs, V 3+ / V 4+ Impurity elements with a standard reduction potential of 0.337 V or higher were the main cause of the pressure increase by inducing the hydrogen generation reaction, and by controlling the concentration of these elements to a low level, the hydrogen generation reaction was suppressed, thereby preventing the pressure from increasing during charging and discharging of the vanadium ion battery.

[0095] Element typeStandard reduction potential value (vs. NHE)Cd-0.4 VIn-0.34 VTi-0.34 VCo-0.277 VV 2+ / V 3+ -0.26 VNi-0.25 VMo-0.2 VSn-0.1375 VPb-0.126 VW-0.12 VFe-0.04 VGe0.12 VSb0.212 VRe0.3 VBi0.308 VV 3+ / V 4+ 0.337 VRu0.45 VCu0.52 VTe0.55 VSe0.74 VAg0.7991 VRh0.8 VOs0.856 VPd0.921 VV 4+ / V 5+ 1 VIr1.16 VPt1.188 VAu1.52 V

[0096] Specifically, V 3+ / V 4+ Among the elements with a standard reduction potential value higher than 0.337 V, which is the standard reduction potential value of , 10 elements including Ru, Cu, Te, Ag, Rh, Os, Pd, Ir, Pt, and Au were confirmed to be impurity elements that induce hydrogen evolution reaction, and the total concentration of these impurity elements was 1.449×10 4 It is desirable to have less than ppb, 3.077×10 3 It is more desirable to have a level below ppb.

[0097] According to one embodiment of the present invention, V 3+ / V 4+ The standard reduction potential value of 0.337 V or higher and V 4+ / V 5+ The total concentration of impurity elements Ru, Cu, Te, Ag, Rh, Os, and Pd, which induce hydrogen evolution reaction among elements with standard reduction potentials less than 1 V, which is the standard reduction potential value of , is 1.257×10 4 It is desirable to have less than ppb, and 2.316×10 3 It is more desirable to have a level below ppb.

[0098] According to one embodiment of the present invention, the total concentration of Ru, Cu and Te, which are impurity elements having a standard reduction potential value of 0.4 V to 0.6 V, among the impurity elements, is 9.888×10 3 It is desirable to have less than ppb, and 1.567×10 3 It is more preferable that it be less than ppb, and at least one of the following conditions (1) to (3) can be satisfied.

[0099] (1) The concentration of ruthenium (Ru) ions is 1.400 × 10 3 Less than ppb, preferably less than 6.980 × 10 2 below ppb

[0100] (2) The concentration of copper (Cu) ions is 1.980 × 10 2 Less than ppb, preferably less than or equal to 3.950 × 10 ppb

[0101] (3) The concentration of teryllium (Te) ions is 8.290 × 10 3 Less than ppb, preferably 8.290 × 10 2 below ppb

[0102] Among the above impurity elements, the total concentration of Ag, Rh, Os, and Pd, which are impurity elements with standard reduction potential values ​​of 0.6 V to 0.8 V, is 1.973×10 3 It is desirable to have less than ppb, 3.769×10 2 It is more preferable that it be less than ppb, and at least one of the following conditions (4) to (7) can be satisfied.

[0103] (4) The concentration of silver (Ag) ions is 2.600 × 10 2 Less than ppb, preferably less than 5.220 × 10 ppb

[0104] (5) The concentration of rhodium (Rh) ions is less than 4.500 ppb, preferably 4.500 × 10 -1 below ppb

[0105] (6) The concentration of osmium (Os) ions is 1.530 × 10 3 Less than ppb, preferably 3.100 × 10 2 below ppb

[0106] (7) The concentration of palladium (Pd) ions is 1.429 × 10 2 Less than ppb, preferably less than or equal to 1.429 × 10 ppb

[0107] According to one embodiment of the present invention, V 4+ / V 5+ The total concentration of Ir, Pt, and Au, which are impurity elements that induce hydrogen evolution reaction among elements with a standard reduction potential value of 1 V or higher, which is the standard reduction potential value of , is 2.662 × 10 3 It is desirable to have less than ppb, and 1.133×10 3 It is more preferable that it be less than ppb, and at least one of the following conditions (8) to (10) can be satisfied.

[0108] (8) The concentration of iridium (Ir) ions is 7.470 × 10 2 Less than ppb, preferably 3.730 × 10 2 below ppb

[0109] (9) The concentration of platinum (Pt) ions is less than 4.500 ppb, preferably 4.500 × 10 -1 below ppb

[0110] (10) The concentration of gold (Au) ions is 1.910 × 10 3 Less than ppb, preferably 7.600 × 10 2 below ppb

[0111]

[0112] According to one embodiment of the present invention, V 2+ / V 3+ The standard reduction potential value of -0.26 V or higher and V 3+ / V 4+ The total concentration of impurity elements Ni and Sb with standard reduction potentials lower than 0.337 V, which is the standard reduction potential of , is 4450×102 Less than ppb, preferably 2280×10 2 A hydrogen generation reaction can be more effectively suppressed by satisfying less than ppb, and at least one of the following conditions (11) to (12) can be satisfied.

[0113] (11) The concentration of nickel (Ni) ions is 2.080 × 10 5 Less than ppb, preferably 1.040 × 10 5 below ppb

[0114] (12) The concentration of antimony (Sb) ions is 2.370 × 10 5 Less than ppb, preferably 1.240 Х 10 5 below ppb

[0115] Like this V 2+ / V 3+ The standard reduction potential value of -0.26 V or higher and V 3+ / V 4+ If we consider the impurity elements with standard reduction potentials lower than 0.337 V, which is the standard reduction potential of hydrogen, the sum of all impurity element ions that cause hydrogen generation is 4.595 × 10 5 Less than ppb, preferably less than 2.311 × 10 5 It may be below ppb.

[0116]

[0117] According to one example of the present invention, the vanadium electrolyte may include vanadium ions and an acidic solution.

[0118] The vanadium ions of the vanadium electrolyte of the present invention can be supplied by vanadium oxide, and the vanadium oxide can include one or more of V2O5, VOSO4, V2O3, NH4VO3, and V2O4, but is not necessarily limited thereto, and can be selected according to electrolyte production conditions, production target amount, etc. The concentration of vanadium ions of the electrolyte including vanadium can be 1.5 M to 3.0 M, and preferably 1.7 M to 2.3 M.

[0119] According to an example 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. 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.

[0120]

[0121] The vanadium electrolyte of the present invention is suitable for pressure-sensitive vanadium ion batteries because the ion concentrations of each element are controlled to very effectively suppress the hydrogen evolution reaction. However, the secondary batteries in which the vanadium electrolyte of the present invention can be used are not limited to vanadium ion batteries, and can naturally be used in conventional vanadium redox flow batteries (VRFBs) that are relatively insensitive to pressure.

[0122]

[0123] Referring to FIGS. 1 to 4, a vanadium ion battery unit cell according to one embodiment of the present invention will be described in detail.

[0124] 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); a negative electrode electrolyte receiving portion (111b) formed between the negative electrode current collector (130b) and the separator (120); a positive electrode solid electrode (150a) disposed in the positive electrode electrolyte receiving portion (111a) and impregnated with the positive electrode electrolyte; and a negative electrode solid electrode (150b) disposed in the negative electrode electrolyte receiving portion (111b) and impregnated with the negative electrode electrolyte.

[0125]

[0126] 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.

[0127]

[0128] A vanadium ion battery unit cell (100) may include a frame (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 frame (110) may be attached to the carbon current collectors of the positive electrode current collector (130a) and the negative electrode current collector (130b) as a support, and due to this structure, a sealed structure may be formed, thereby ensuring the airtightness required for a vanadium ion battery.

[0129] In the present invention, the frame (110) may be a metal frame or a plastic frame, and according to one embodiment, may be a plastic frame. The plastic for forming the plastic frame may be a styrene-based plastic. Specific types of the plastic may be selected from polystyrene (PS), high impact polystyrene (HIPS), styrene acrylonitrile (AS), and acrylonitrile butadiene styrene (ABS), and preferably acrylonitrile butadiene styrene (ABS).

[0130]

[0131] An electrolyte containing vanadium ions as the positive electrolyte and the negative electrolyte can be supplied to each of the positive electrolyte receiving portion (111a) and the negative electrolyte receiving portion (111b).

[0132]

[0133] 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 cloth, 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).

[0134]

[0135] 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 frame (110).

[0136] 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.

[0137] 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.

[0138] 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 volume.

[0139]

[0140] The separator (120) of the vanadium ion battery unit cell (100) of the present invention may include a hydrocarbon-based separator including a cation-conducting hydrocarbon-based polymer. Nafion, which has been commonly used ® Since it is formed of a fluorine-based cation-conducting polymer, it has the disadvantage of being vulnerable to contamination of the secondary battery as it can leak halogen substances. In addition, in a secondary battery using an aqueous electrolyte (called an 'aqueous secondary battery'), protons (H) in the electrolyte + ) may generate pressure inside the cell of the secondary battery due to microfluidic movement and side reactions (generation of gases such as H2 and CO2) that commonly occur in aqueous secondary 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.

[0141] The hydrocarbon-based separation membrane may be formed from 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.

[0142] 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 membrane made of polypropylene (PP) or polyethylene (PE) may be selected, but is not necessarily limited thereto.

[0143] The above hydrocarbon polymer may include any one of a polyimide polymer, a polyetheretherketone polymer, a polyethersulfone polymer, and a polybenzimidazole polymer.

[0144]

[0145] Referring to FIG. 2, 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).

[0146] 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.

[0147] 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 the 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).

[0148] Hereinafter, the present invention will be described in more detail by describing manufacturing examples and experimental examples. However, these are merely examples of the present invention and the present invention is not limited thereto.

[0149]

[0150] Manufacturing Example 1 - Fabrication of a secondary battery unit cell

[0151] A unit cell of a secondary battery having a size of 99 mm × 99 mm was manufactured by stacking a first metal current collector - a first carbon current collector - a first solid electrode - a separator - a second solid electrode - a second carbon current collector - a second metal current collector in that order on a frame (ABS material, 15 mm) and then sealing it. The materials used in manufacturing the unit cell are as follows.

[0152] - First and second solid electrodes: carbon felt (thickness: 5 mm)

[0153] - First and second metal collectors: Aluminum collector (thickness: 0.2 mm)

[0154] - First and second carbon collectors: graphite sheet (thickness: 0.2 mm)

[0155] - Membrane: Polybenzimidazole-based membrane

[0156] The manufacturing method of the above separation membrane is as follows.

[0157] After adding m-PBI, a polybenzimidazole precursor, to dimethyl acetamide (DMAC), the solution was dissolved while stirring at 160°C and atmospheric pressure for 24 hours to produce a PBI solution with a maximum dissolution rate of 12 wt%. Then, a PE film (thickness: 20 μm) was impregnated into the PBI solution, and then dried with hot air at 50°C for 2 minutes to obtain a separator with a thickness of 27 μm.

[0158]

[0159] Manufacturing Example 2 - Manufacturing of a reference electrolyte

[0160] In order to determine whether pressure is generated according to the concentration of each sample, a "reference electrolyte" was prepared to be used as a standard for which no pressure is generated. The reference electrolyte was a vanadium electrolyte (1.7 M V 3.5+ , 1.7M sulfuric acid aqueous solution) was used to conduct a charge and discharge test for approximately 700 hours under the following charge and discharge conditions using the unit cell manufactured in the above manufacturing example, and it was confirmed that no pressure was generated.

[0161] [Charge / Discharge Conditions]

[0162] - Charging: Charge with a current of 1.0 C until the charge energy reaches 2 Wh.

[0163] - Rest after charging: 100 seconds

[0164] - Discharge: Discharge at a constant current of 1.0 C until the voltage reaches 1.10 V.

[0165]

[0166] Experimental example

[0167] Samples were added to the above standard electrolyte to provide 12 types of element ions, and the samples for the target element ions are shown in Table 2 below.

[0168] No. Target Elements Samples Used 1 Nickel (Ni) Nickel (II) sulfate 2 Copper (Cu) Copper (II) sulfate 3 Ruthenium (Ru) Ru (III) Cl 2-2.5% in HCl (10%-20%) 4 Rhodium (Rh) Rhodium (III) chloride 0.2% in HCl (3.6%) 5 Palladium (Pd) Pd (II) Cl 2 0.025% in HCl (5%) 6 Osmium (Os) OsO 4 (2.5-5%) in H2O (95-97.5%) 7 Iridium (Ir) Iridium (III) chloride 8 Platinum (Pt) H2 PtCl 6 (0.2%) in HCl (3.6%) 9 Silver (Ag) Silver (I) sulfate 10 Gold (Au) Gold metal in 5% HCl 11 Antimony (Sb) Antimony (III) chloride, SbCl312Tellurium(IV) dioxide, TeO2

[0169] In the following experiments, added samples with concentrations below 1 ppm were diluted to produce a higher-concentration solution, which was then used in the experiments. The ICP-OES measurement range was ppb to ppm, and the concentrations of the corresponding element ions used in the experiments were measured.

[0170] Experimental Example 1 - Concentration Experiment for Ruthenium (Ru)

[0171] Ru(III)Cl32-2.5% in HCl (10%-20%) was added to the reference electrolyte so that the concentration of ruthenium ions became 826 ppm, and the vanadium ion battery unit cell manufactured in Manufacturing Example 1 was used to conduct the first charge / discharge experiment for 25 cycles under the charge / discharge conditions of Manufacturing Example 2, while checking whether pressure was generated in the vanadium ion battery unit cell. If pressure was generated, the concentration of ruthenium ions was gradually lowered and the experiment was continued until a concentration at which no pressure was generated was confirmed.

[0172] For samples that did not generate pressure in the first charge / discharge experiment of 25 cycles, a second charge / discharge experiment of 250 cycles was conducted to verify the pressure and presence / absence of pressure according to the concentration at which pressure was not generated.

[0173] The criteria for determining that pressure has been generated are as follows: if the pressure measured while repeating charge and discharge for a vanadium ion battery unit cell exceeds 80 kPa, it is determined that pressure has been generated (indicated as "O"); otherwise, it is determined that pressure has not been generated (indicated as "X"), as shown in Table 2 below.

[0174] A pressure gauge was attached to the electrolyte inlet to measure pressure. The pressure gauge used in this experiment was manufactured by Sensys, and the measurement pressure range was -100 kPa to 100 kPa, and the accuracy (display) was ±0.5% FS (25 ℃).

[0175] The results of the above experiment are shown in Table 3, Fig. 6a and Fig. 6b below.

[0176] Concentration pressure generationPressure (kPa)0.175 ppmX-10 ~ -40.349 ppmX-10 ~ -40.698 ppmX10 ~ 201.40 ppmO↑80

[0177] From the above Table 3, Figures 6a and 6b, the ion concentration of ruthenium element is at least 1.40 ppm (1.400 × 10 3 ppb) and the ruthenium element ion concentration must be less than 0.698 ppm (6.980 × 10 2 It was confirmed that no pressure was generated when the concentration was below ppb.

[0178] Experimental Example 2 - Concentration Experiment for Copper (Cu)

[0179] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the copper ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the copper element ion concentration are shown in Table 4, Figures 7a and 7b below.

[0180] Concentration pressure generationPressure (kPa)19.8 ppbX-20 ~ -1039.5 ppbX-10 ~ 00.198 ppmO↑800.989 ppmO↑80

[0181] From the above Table 4, Figures 7a and 7b, the ion concentration of copper element is at least 0.198 ppm (1.980 × 10 2 It must be satisfied that the concentration of copper element ions is less than 39.5 ppb (3.950 × 10 ppb), and it was confirmed that no pressure is generated when the concentration of copper element ions is less than 39.5 ppb (3.950 × 10 ppb).

[0182] Experimental Example 3 - Concentration Experiment on Teryllium (Te)

[0183] An experiment was conducted using the same method as Experimental Example 1 using a sample for confirming the concentration of teryllium ions in Table 2 above, and the pressure and presence or absence of pressure generation according to the concentration of teryllium element ions are shown in Table 5, Figures 8a and 8b below.

[0184] Concentration pressure generationPressure (kPa)0.829 ppmX5 ~ 158.29 ppmO↑8074.8 ppmO↑80800 ppmO↑80

[0185] From the above Table 5, Figures 8a and 8b, the ion concentration of the element teryllium is at least 8.29 ppm (8.290 × 10 3 ppb) and the teryllium element ion concentration must be less than 0.829 ppm (8.290 × 10 2 It was confirmed that no pressure was generated when the concentration was below ppb.

[0186] Experimental Example 4 - Concentration Experiment for Silver (Ag)

[0187] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the silver ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the silver element ion concentration are shown in Table 6, Figures 9a and 9b below.

[0188] Concentration pressure generationPressure (kPa)10.4 ppbX-10 ~ 052.2 ppbX10 ~ 200.26 ppmO↑800.52 ppmO↑801.04 ppmO↑802.09 ppmO↑804.18 ppmO↑808.35 ppmO↑80

[0189] From the above Table 6, Figures 9a and 9b, the ion concentration of silver element is at least 0.26 ppm (2.600 × 10 2 It must be satisfied that the concentration is less than 52.2 ppb (5.220 × 10 ppb), and it was confirmed that no pressure is generated when the concentration of silver element ions is less than 52.2 ppb (5.220 × 10 ppb).

[0190] Experimental Example 5 - Concentration Experiment for Rhodium (Rh)

[0191] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the rhodium ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the rhodium element ion concentration are shown in Table 7, Figures 10a and 10b below.

[0192] Concentration pressure generationPressure (kPa)0.45 ppbX-20 ~ -104.50 ppbO↑808.99 ppbO↑8022.48 ppbO↑8044.96 ppbO↑80

[0193] From the above Table 7, Fig. 10a and Fig. 10b, it must be satisfied that the ion concentration of the rhodium element is at least less than 4.50 ppb (4.500 ppb), and the rhodium element ion concentration is 0.45 ppb (4.500 × 10 -1 It was confirmed that no pressure was generated when the concentration was below ppb.

[0194] Experimental Example 6 - Concentration Experiment for Osmium (Os)

[0195] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the osmium ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the osmium element ion concentration are shown in Table 8, Figures 11a and 11b below.

[0196] Concentration pressure generationPressure (kPa)0.31 ppmX0 ~ 101.53 ppmO↑807.67 ppmO↑80

[0197] From the above Table 8, Figures 11a and 11b, the ion concentration of osmium element is at least 1.53 ppm (1.530 × 10 3 ppb) and the osmium element ion concentration must be less than 0.31 ppm (3.100 × 10 2 It was confirmed that no pressure was generated when the concentration was below ppb.

[0198] Experimental Example 7 - Concentration Experiment for Palladium (Pd)

[0199] An experiment was conducted using the same method as Experimental Example 1 using a sample for confirming the palladium ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the palladium element ion concentration are shown in Table 9, Figures 12a and 12b below.

[0200] Concentration pressure generationPressure (kPa)14.29 ppbX30 ~ 40142.9 ppbO↑801.43 ppmO↑80

[0201] From the above Table 9, Figures 12a and 12b, the ion concentration of palladium element is at least 142.9 ppb (1.429 × 10 2 It must be satisfied that the concentration of palladium element ions is less than 14.29 ppb (1.429 × 10 ppb), and it was confirmed that no pressure is generated when the palladium element ion concentration is less than 14.29 ppb (1.429 × 10 ppb).

[0202] Experimental Example 8 - Concentration Experiment for Iridium (Ir)

[0203] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the iridium ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the iridium element ion concentration are shown in Table 10, Figures 13a and 13b below.

[0204] Concentration pressure generationPressure (kPa)0.187 ppmX-10 ~ 00.373 ppmX0 ~ 100.747 ppmO↑80

[0205] From the above Table 10, Figures 13a and 13b, the ion concentration of iridium element is at least 0.747 ppm (7.470 × 10 2 ppb) and the iridium element ion concentration must be less than 0.373 ppm (3.730 × 10 2 It was confirmed that no pressure was generated when the concentration was below ppb.

[0206] Experimental Example 9 - Concentration Experiment for Platinum (Pt)

[0207] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the platinum ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the platinum element ion concentration are shown in Table 11, Figures 14a and 14b below.

[0208] Concentration pressure generationPressure (kPa)0.45 ppbX-30 ~ -254.50 ppbO↑808.99 ppbO↑8022.48 ppbO↑8044.96 ppbO↑80

[0209] From the above Table 11, Figures 14a and 14b, it must be satisfied that the ion concentration of the platinum element is at least less than 4.50 ppb (4.500 ppb), and the platinum element ion concentration is 0.45 ppb (4.500 × 10 -1 It was confirmed that no pressure was generated when the concentration was below ppb.

[0210] Experimental Example 10 - Concentration Experiment for Gold (Au)

[0211] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the gold ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the gold element ion concentration are shown in Table 12, Figures 15a and 15b below.

[0212] Concentration pressure generationPressure (kPa)0.76 ppmX-10 ~ 01.91 ppmO↑803.82 ppmO↑807.63 ppmO↑80

[0213] From the above Table 12, Figures 15a and 15b, the ion concentration of gold element is at least 1.91 ppm (1.910 × 10 3 ppb) and the gold element ion concentration must be less than 0.76 ppm (7.600 × 10 2 It was confirmed that no pressure was generated when the concentration was below ppb.

[0214] Experimental Example 11 - Concentration Experiment for Nickel (Ni)

[0215] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the nickel ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the nickel element ion concentration are shown in Table 13, Figures 16a and 16b below.

[0216] Concentration pressure generationPressure (kPa)52 ppmX-20 ~ -10104 ppmX10 ~ 20208 ppmO↑80425 ppmO↑80826 ppmO↑80

[0217] From the above Table 13, Figs. 16a and 16b, the ion concentration of nickel element is at least 208 ppm (2.080 × 10 5 ppb) and the nickel element ion concentration must be less than 104 ppm (1.040 × 10 5 It was confirmed that no pressure was generated when the concentration was below ppb.

[0218] Experimental Example 12 - Concentration Experiment for Antimony (Sb)

[0219] An experiment was conducted using the same method as Experimental Example 1 using the sample for confirming the antimony ion concentration in Table 2 above, and the pressure and presence or absence of pressure generation according to the antimony element ion concentration are shown in Table 14, Figures 17a and 17b below.

[0220] Concentration pressure generationPressure (kPa)124 ppmX0 ~ 10237 ppmO↑80449 ppmO↑80

[0221] From the above Table 14, Figures 17a and 17b, the ion concentration of antimony element is at least 237 ppm (2.370 × 10 5 ppb) and the antimony element ion concentration must be less than 124 ppm (1.240× 10 5 It was confirmed that no pressure was generated when the concentration was below ppb.

[0222] Referring to the above experimental examples 1 to 12, including vanadium ions, V 3+ / V 4+ It can be seen that impurity elements (except vanadium) with a standard reduction potential value of 0.337 V or higher, which is the standard reduction potential value of hydrogen, are the main factors inducing the hydrogen evolution reaction, and the total concentration of these impurity elements is 1.449×10 4 It is desirable to have less than ppb, 3.077×10 3 It was experimentally confirmed that a value below ppb is more desirable, and when this condition is satisfied, the effect of suppressing pressure generation by hydrogen gas can be exhibited.

[0223] Furthermore, among the element ions that can cause hydrogen generation, V 2+ / V 3+ The standard reduction potential value of -0.26 V or higher and V 3+ / V 4+ The total concentration of impurity elements Ni and Sb with standard reduction potentials lower than 0.337 V, which is the standard reduction potential of , is 4450×10 2 Less than ppb, preferably 2280×10 2It was confirmed that satisfying less than ppb can more effectively suppress the hydrogen evolution reaction.

[0224] 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.

Claims

1. Contains vanadium ions, V 3+ / V 4+ The total concentration of impurity elements with a standard reduction potential value higher than 0.337 V, which is the standard reduction potential value of , is 1.449×10 4 is less than ppb, The above impurity element does not contain vanadium (V). Vanadium electrolyte.

2. In paragraph 1, V 3+ / V 4+ The standard reduction potential value of 0.337 V or higher and V 4+ / V 5+ The total concentration of impurity elements with standard reduction potentials less than 1 V, which is the standard reduction potential of , is 1.257×10 4 Less than ppb, Vanadium electrolyte.

3. In paragraph 1, V 4+ / V 5+ The total concentration of impurity elements with a standard reduction potential greater than 1 V, which is the standard reduction potential of , is 2.662 × 10 3 Less than ppb, Vanadium electrolyte.

4. In paragraph 1, The total concentration of impurity elements with standard reduction potentials of 0.4 V to 0.6 V is 9.888×10 3 Less than ppb, Vanadium electrolyte.

5. In paragraph 4, Satisfying at least one of the following conditions (1) to (3): Vanadium electrolyte. (1) The concentration of ruthenium (Ru) ions is 1.400 × 10 3 less than ppb (2) The concentration of copper (Cu) ions is 1.980 × 10 2 less than ppb (3) The concentration of teryllium (Te) ions is 8.290 × 10 3 less than ppb 6. In paragraph 1, The total concentration of impurity elements with standard reduction potentials of 0.6 V to 0.8 V is 1.937×10 3 Less than ppb, Vanadium electrolyte.

7. In paragraph 6, Satisfying at least one of the following conditions (4) to (7), Vanadium electrolyte. (4) The concentration of silver (Ag) ions is 2.600 × 10 2 less than ppb (5) The concentration of rhodium (Rh) ions is less than 4.500 ppb. (6) The concentration of osmium (Os) ions is 1.530 × 10 3 less than ppb (7) The concentration of palladium (Pd) ions is 1.429 × 10 2 less than ppb 8. In paragraph 3, Satisfying at least one of the following conditions (8) to (10), Vanadium electrolyte. (8) The concentration of iridium (Ir) ions is 7.470 × 10 2 less than ppb (9) The concentration of platinum (Pt) ions is less than 4.500 ppb. (10) The concentration of gold (Au) ions is 1.910 × 10 3 less than ppb 9. In paragraph 1, V 2+ / V 3+ The standard reduction potential value of -0.26 V or higher and V 3+ / V 4+ The total concentration of impurity elements with standard reduction potentials lower than 0.337 V, which is the standard reduction potential of , is 4450×10 2 I am more satisfied with less than ppb, Vanadium electrolyte.

10. In paragraph 9, Satisfying at least one of the following conditions (11) to (12), Vanadium electrolyte. (11) The concentration of nickel (Ni) ions is 2.080 × 10 5 less than ppb (12) The concentration of antimony (Sb) ions is 2.370 × 10 5 less than ppb 11. In paragraph 1, The above vanadium ions are supplied by vanadium oxides including one or more of V2O5, VOSO4, V2O3, NH4VO3 and V2O4. Vanadium electrolyte.

12. In paragraph 1, The above vanadium electrolyte comprises an acidic solution containing at least one of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid. Vanadium electrolyte.

13. Containing 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 cathode electrolyte receiving portion formed between the cathode current collector and the separator; A negative electrode electrolyte receiving portion formed between the negative electrode current collector and the separator; A positive electrode solid electrode disposed in the positive electrode electrolyte receiving portion and impregnated with the positive electrode electrolyte; and A cathode solid electrode disposed in the cathode electrolyte receiving portion and impregnated with the cathode electrolyte; 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 is a vanadium electrolyte according to any one of claims 1 to 12. Vanadium ion battery.

14. In paragraph 13, 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.

15. In paragraph 13, 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.

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