A low-cost liquid flow battery and its application

Abstract

The application provides a low-cost flow battery and application thereof, and the low-cost flow battery contains a hydroxylamine cyclic structure group with a hindered amine in a redox active material of a positive electrolyte of the low-cost flow battery, the hydroxylamine cyclic structure group with the hindered amine is preferably one or more of a 1-hydroxyl-2,2,6,6-tetrasubstituted piperidine group, a 1-oxygen radical-2,2,6,6-tetrasubstituted piperidine group and a 1-oxo-2,2,6,6-tetrasubstituted piperidinium group; and the redox active material of a negative electrolyte of the low-cost flow battery contains one or more of titanium elements, vanadium elements, chromium elements, iron elements and zinc elements. The low-cost flow battery has the advantages of high output voltage, high energy density, environmental friendliness and low cost, and has good application prospect and large-scale promotion potential in the field of energy storage.

Description

TECHNICAL FIELD

[0001] The present application relates to the organic liquid flow battery technology, and particularly relates to a low-cost liquid flow battery and application thereof. BACKGROUND

[0002] Redox flow battery (RFB) is a kind of storage device for converting electrical energy and chemical energy, mainly suitable for fixed energy storage applications, such as a buffer battery for wind power plants and solar power plants or a power and regulation reserve for load distribution in the power network, and as a mobile energy storage device, or for running electric vehicles and electronic devices. During the charging or discharging process of the battery, the active substances in the positive electrolyte and the active substances in the negative electrolyte are converted into their respective redox states; the positive and negative electrolytes are pumped out of the respective tanks and pumped into the respective reaction chambers. The positive chamber and the negative chamber in the stack are separated by an ion-selective diaphragm, which usually has high selectivity for corresponding ions (such as Nafion membrane). In addition, there are size-selective diaphragms (such as dialysis membranes or ultrafiltration membranes) that allow anions or cations to pass through.

[0003] With the continuous expansion of the scale of renewable energy power generation such as solar energy and wind energy, the intermittency and instability problems are increasingly prominent. As a large-scale energy storage technology, redox flow battery can store electrical energy when the power of renewable energy generation is excessive and release electrical energy when the power of renewable energy generation is insufficient, thereby playing a role in smoothing output and stabilizing the power grid. However, the traditional redox flow battery has low energy density, which is difficult to meet the demand of large-scale energy storage, and the low voltage limits its overall performance. Therefore, in order to adapt to the continuous expansion of the scale of renewable energy power generation, it is urgent to develop a new type of redox flow battery with high voltage and high energy density. SUMMARY

[0004] The purpose of the present application is to solve the above problems, and to provide a low-cost liquid flow battery, which has the advantages of high output voltage, high energy density, environmental friendliness and low cost, and has good application prospect and large-scale promotion potential in the field of energy storage.

[0005] It should be noted that in the present application, unless otherwise specified, the specific meaning of "including" involved in the composition limitation and description includes both the open "including", "containing" and the like and their similar meanings, and the closed "consisting of", "consisting of" and the like and their similar meanings.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is: a low-cost liquid flow battery, wherein the redox active substance of the positive electrolyte contains a hydroxylamine cyclic structure group with a hindered amine.

[0007] Further, the redox active material of the negative electrolyte contains one or more of titanium, vanadium, chromium, iron and zinc elements.

[0008] Another object of the present application also discloses the application of low-cost flow batteries in mobile and stationary energy storage.

[0009] The low-cost flow battery and its application of the present application have the following advantages compared with the prior art:

[0010] 1) The open-circuit voltage of the single string low-cost flow battery exceeds 1.35V, which is significantly higher than that of the traditional iron-chromium flow battery. Higher open-circuit voltage means that the battery can provide greater output power under the same current conditions, which is particularly important for application scenarios that require high power output. In addition, high voltage design can also reduce the number of battery strings, thereby simplifying the structural design and subsequent maintenance of the battery system.

[0011] 2) The low-cost flow battery of the present application has significant environmental friendly characteristics. The battery system avoids the use of toxic chemicals, meeting the urgent demand for green energy and environmental protection technology.

[0012] 3) Energy density is one of the important indicators to measure the performance of the battery. The TEMPO-based flow battery usually only uses its single electron characteristics. The redox active material of the positive electrolyte of the present application can charge and discharge 2 electrons per molecule, greatly improving the energy density, up to 30-300Wh / L.

[0013] 4) The low-cost flow battery of the present application has significant cost advantage, as it does not rely on rare metals, effectively reducing the production cost of the battery and enhancing the market competitiveness. This innovation not only helps to promote the widespread application in large-scale energy storage field, but also provides an economically viable solution for sustainable energy storage.

[0014] 5) The low-cost flow battery of the present application has some paired as a dual-flow battery, which is a non-deposited battery with fully decoupled power and capacity. The electrolyte of the positive and negative electrodes of the dual-flow battery is stored in different liquid storage tanks, and the electrolyte is driven by the pump to react in the battery stack. This design helps to improve the flexibility and scalability of the battery system; power and capacity can be designed independently to meet the needs of different application scenarios. Specifically, in high power output scenarios, the power can be increased by increasing the number of battery stacks; while in long-term energy storage scenarios, larger capacity energy storage can be achieved by increasing the electrolyte capacity. This modular design concept enables the battery system to be flexibly configured according to actual needs, which has significant application advantages.

[0015] In summary, the low-cost liquid flow battery of the present application can be operated safely, economically and effectively, and has significant advantages in voltage output, environmental friendliness, energy density, cost and system flexibility, and has good application prospect and large-scale promotion potential in the field of energy storage. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A test device diagram;

[0017] Figure 2 Charge-discharge curve of the battery of Example 1 over time;

[0018] Figure 3 Charge-discharge curve of the battery of Example 2 over time;

[0019] Figure 4 Charge-discharge efficiency curve of the battery of Example 2

[0020] Figure 5 Energy efficiency curve of the battery of Example 2;

[0021] Figure 6 Discharge capacity curve of the battery of Example 2;

[0022] Figure 7 Charge-discharge curve of the battery of Example 3 over time;

[0023] Figure 8 Charge-discharge efficiency curve of the battery of Example 3

[0024] Figure 9 Energy efficiency curve of the battery of Example 3;

[0025] Figure 10 Discharge capacity curve of the battery of Example 3. DETAILED DESCRIPTION

[0026] The present application relates to a liquid flow battery for storing electrical energy through the oxidation-reduction of chemical media, namely a redox flow battery (also known as a redox battery or a redox flow battery). The core structure of the system is composed of an electric pile, which contains multiple groups of reaction sheets arranged in series or parallel, each group of reaction sheets is provided with a positive electrode chamber (cathode) and a negative electrode chamber (anode), and the two chambers are physically isolated by an ion exchange membrane or diaphragm. The positive electrode chamber is defined as extending from the positive electrode to the diaphragm region facing the positive electrode, and the negative electrode chamber is defined as extending from the negative electrode to the diaphragm region facing the negative electrode. Each chamber is connected to the corresponding liquid storage tank through an independent circulation loop: the positive electrode chamber and the positive electrode liquid storage tank form a closed loop system, and the negative electrode chamber and the negative electrode liquid storage tank form another independent closed loop system, and the two systems are ionically conductive but physically isolated by the diaphragm.

[0027] The chambers and reservoirs store electrolytes containing redox active materials in dissolved or dispersed form in electrolyte solvents, with optional addition of conductive salts and other functional additives to optimize electrochemical performance. During charge and discharge, the positive and negative electrolytes undergo reversible reactions in the corresponding chambers: during charge, the positive active material undergoes oxidation in the positive chamber and the negative active material undergoes reduction in the negative chamber; during discharge, the reactions reverse, and the positive active material is reduced and the negative active material is oxidized. Ions migrate directionally through the separator to maintain charge balance, while the redox reactions of the active materials at the electrode surfaces enable storage and release of electrical energy through the external circuit.

[0028] The energy storage capacity of the system is determined by the total amount of active materials in the positive and negative electrolytes, while the output power depends on the effective reaction area formed by the multiple sets of reaction sheets in the stack. This decoupling of energy and power allows the flow battery to be flexibly adapted to different application scenarios by independently adjusting the reservoir volume (to control capacity) and the stack size (to control power).

[0029] The low-cost flow battery of the present application has a positive electrolyte containing a redox active material of the formula Y:

[0030]

[0031] Formula Y is a hydroxylamine cyclic structure group with a hindered amine, the cyclic structure being a 3-membered ring, a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring, or an 8-membered ring;

[0032] The cyclic structure contains one or more of a carbon-carbon single bond, a carbon-carbon double bond, and a carbon-carbon triple bond;

[0033] R1, R2, R3, and R4 are each independently selected from alkyl, cycloalkyl, aryl, and aralkyl.

[0034] Further, the cyclic structure can be connected to the remaining molecular structure through an introduced covalent bond, and one or more of, for example, methyl, propyl, and phenyl groups can be attached to the ring, with no limit on the number of groups attached.

[0035] The hydroxylamine cyclic structure group with a hindered amine can undergo a highly reversible redox reaction of the formula Ya, and the reversible conversion between the hydroxylamine, nitroxyl radical, and nitroxonium salt is one of the cores disclosed and protected by the present application, so that a single hydroxylamine cyclic structure group of a hindered amine can charge and discharge 2 electrons.

[0036] Further, the hindered amine hydroxylamine cyclic structure group is one or more of a 1-hydroxy-2,2,6,6-tetrasubstituted piperidinyl group, a 1-hydroxy-2,2,5,5-tetrasubstituted pyrrolyl group, and a 1-hydroxy-2,2,5,5-tetrasubstituted pyrrolinyl group; all of which can undergo reversible redox reactions as shown in Formula Ya, with 2-electron charge-discharge characteristics.

[0037] Further, the most preferred hindered amine hydroxylamine cyclic structure group is a 1-hydroxy-2,2,6,6-tetrasubstituted piperidinyl group, which is the lowest cost.

[0038]

[0039] Further, the described positive electrolyte redox active material contains one or more of a 1-hydroxy-2,2,6,6-tetrasubstituted piperidinyl group, a 1-oxyl-2,2,6,6-tetrasubstituted piperidinyl group, and a 1-oxo-2,2,6,6-tetrasubstituted piperidinium group; and the negative electrolyte redox active material contains one or more of titanium, vanadium, chromium, iron, and zinc elements.

[0040] The reaction occurring at the positive electrode during the charge-discharge process of the low-cost flow battery of the present application is as follows:

[0041]

[0042] The 1-hydroxy-2,2,6,6-tetrasubstituted piperidinyl unit loses a proton and an electron during the charging process, and is converted into a 1-oxyl-2,2,6,6-tetrasubstituted piperidinyl unit; when the charging continues, the 1-oxyl-2,2,6,6-tetrasubstituted piperidinyl unit loses an electron and is oxidized into a 1-oxo-2,2,6,6-tetrasubstituted piperidinium unit. During the discharging process, the 1-oxo-2,2,6,6-tetrasubstituted piperidinium unit is sequentially reduced into a 1-oxyl-2,2,6,6-tetrasubstituted piperidinyl unit and a 1-hydroxy-2,2,6,6-tetrasubstituted piperidinyl unit. The above formula shows the redox equilibrium between the 1-hydroxy-2,2,6,6-tetrasubstituted piperidinyl unit, the 1-oxyl-2,2,6,6-tetrasubstituted piperidinyl unit, and the 1-oxo-2,2,6,6-tetrasubstituted piperidinium unit during the charging process / discharge process.

[0043] The reaction occurring at the negative electrode during the charge-discharge process of the low-cost flow battery of the present application is as follows:

[0044]

[0045] During the charging process, metal cations in the negative electrode electrolyte are reduced to corresponding low-valent metal cations or metal elements on the negative electrode surface; during the discharge process, the reduced metal cations or metal elements are oxidized to higher-valent metal cations. The above formula shows the redox equilibrium of metal cations or metal elements during the charging / discharging process. When the negative electrode active material is titanium cations, during charging, titanium (IV) cations are sequentially reduced to titanium (III) cations and titanium (II) cations on the negative electrode surface; during discharge, titanium (III) cations and titanium (II) cations are sequentially oxidized to titanium (IV) cations on the negative electrode surface, and titanium cations can be used as two-electron active materials. When the negative electrode active material is vanadium cations, during charging, vanadium (IV) cations are sequentially reduced to vanadium (III) cations and vanadium (II) cations on the negative electrode surface; during discharge, vanadium (III) cations and vanadium (II) cations are sequentially oxidized to vanadium (IV) cations on the negative electrode surface, and vanadium cations can be used as two-electron active materials. When the negative electrode active material is a chromium cation, during charging, the chromium (III) cation is reduced to a chromium (II) cation on the negative electrode surface; during discharge, the chromium (II) cation is oxidized to a chromium (III) cation on the negative electrode surface. When the negative electrode active material is an iron (II) cation, during charging, the iron (II) cation is reduced to elemental iron (0) on the negative electrode surface; during discharge, the elemental iron (0) is oxidized to an iron (II) cation on the negative electrode surface. The iron cation can be used as a two-electron active material. When the negative electrode active material is a zinc (II) cation, during charging, the zinc (II) cation is reduced to elemental zinc (0) on the negative electrode surface; during discharge, the elemental zinc (0) is oxidized to zinc (II) cation on the negative electrode surface. The zinc cation can be used as a two-electron active material. Of course, the negative electrode can also be a mixture of titanium ions, vanadium ions, chromium ions, iron ions, elemental iron, zinc ions, or elemental zinc. Of course, these metal cations or metal elements can act as conductive additives or act as part of conductive additives. In the case of elemental iron or zinc, the elemental iron solid negative electrode or elemental zinc solid negative electrode can be permanently present as a metal electrode, but can also be formed in situ in the chamber by reducing the iron or zinc cations on the conductive surface, even just during the charging process of the battery.

[0046] Although the 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group, the 1-oxy-2,2,6,6-tetrasubstituted piperidine group, and the 1-oxo-2,2,6,6-tetrasubstituted piperidinium group are different substances, there is a high degree of charge and discharge reversibility between these three groups. For the convenience of the following writing and description, the following description is only based on the 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group as the starting material. Of course, the 1-oxy-2,2,6,6-tetrasubstituted piperidine group, the 1-oxo-2,2,6,6-tetrasubstituted piperidinium group, and any combination of the three are also included in the present invention.

[0047] The redox active substance of the positive electrode electrolyte is a 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group. Its preferred representative is a 1-hydroxy-2,2,6,6-tetramethylpiperidine group. The 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group can be used as a low molecular weight compound or as a component of an oligomeric compound (also known as an oligomer), and can also be used as part of a high molecular weight compound (also known as a polymer). In the latter case, the 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group unit is located in the side chain of the polymer. In addition to the side chain of the redox active unit, the macromolecule itself can also carry other side chains, for example, to improve solubility in the electrolyte. In addition to 2,2,6,6-tetrasubstituted, the hydroxypiperidine unit can also be modified by other substituents.

[0048] The positive electrode electrolyte may contain molecules having 1-hydroxy-2,2,6,6-tetrasubstituted-piperidinyl groups in the form of a solution or dispersion in an aqueous or aqueous-organic electrolyte. Alternatively, the molecules having 1-hydroxy-2,2,6,6-tetrasubstituted-piperidinyl groups may be liquid compounds.

[0049] The positive electrode electrolyte contains a compound containing at least one group of formula I as a redox active component:

[0050]

[0051] The line leaving position 4 in the structure of Formula I represents a covalent bond, and the structure of Formula I is connected to the rest of the compound molecule via a covalent bond at position 4, and R1, R2, R3, and R4 are independently selected from alkyl, cycloalkyl, aryl, and aralkyl groups. As described above, the group of Formula I can be part of a low molecular weight compound, an oligomeric compound, or a high molecular weight compound. Position 1 above is the position of the nitrogen atom. Counting clockwise, R1 and R2 are located at position 2, position 4 corresponds to the fourth carbon atom on the ring, and R3 and R4 are located at position 6.

[0052] In the context of the present description, a “low molecular weight compound” is understood to be a compound which has no repeating structural units derived from monomers and which contains at least 1, preferably 1 to 6, particularly preferably 1 to 4, in particular 1 to 3 and very particularly preferably 1 or 2 groups of the formula I.

[0053] In the context of the present description, “oligomeric compounds” are understood to be compounds which have 2 to 10 repeating structural units derived from monomers, each of which carries one radical of the formula I.

[0054] “High molecular weight compounds” in the context of this specification are understood to be compounds which have more than 10, preferably 11 to 15, repeating structural units derived from monomers, each of which carries one radical of the formula I.

[0055] The positive electrode electrolyte has as redox-active components compounds having 1 to 6, preferably 1 to 4, in particular 1 to 3, and very particularly preferably 1 to 2 groups of the formula I in the molecule.

[0056] The positive electrode electrolyte comprises a compound having one or more of Formulas Ia, Ib, Ic, Id, Ie and If as a redox active component:

[0057]

[0058]

[0059] In formulas Ia, Ib, Ic, Id, Ie and If, R1, R2, R3 and R4 have the same meanings as defined for formula I, X represents a q-valent inorganic or organic anion or a mixture of anions of this type, q is an integer from 1 to 3, o is an integer from 1 to 4, u is an integer from 1 to 4, R8 is a divalent to tetravalent organic bridging group, R5 is hydrogen, alkyl, alkoxy, haloalkyl, cycloalkyl, aryl, aralkyl, heterocyclyl, halogen, hydroxyl, amino, nitro or cyano, and R6 is a single positive ion with o valence, preferably a single positive ion with o valence. R9 is a divalent to tetravalent organic group with an m-fold positive charge, especially a divalent to tetravalent quaternary ammonium group, a divalent to tetravalent quaternary phosphonium group, a divalent to trivalent tertiary sulfonium group, or a divalent to tetravalent heterocyclic group with an m-fold positive charge, R7 is a monovalent group with a u-fold, preferably a single negative charge, especially a carboxyl group or a sulfonic acid group, or a monovalent heterocyclic group with a u-fold, preferably a single negative charge, R 10 is a divalent to tetravalent organic group having an m-fold negative charge, in particular an alkylene group substituted by 1 or 2 carboxyl or sulfonic acid groups, or a phenylene group substituted by 1 or 2 carboxyl or sulfonic acid groups, or a divalent heterocyclic group substituted by 1 or 2 carboxyl or sulfonic acid groups, Z is a q-valent inorganic or organic cation or a mixture of cations of this type, f is an integer from 1 to 3, l is a number having the value o / q or u / q, m is an integer from 1 to 4, and n represents a number having the value m / q.

[0060] The redox-active component is an oligomer or polymer having a backbone comprising a plurality of redox-active units of formula I as defined above.

[0061] The redox-active component is an oligomer or polymer having a backbone comprising a plurality of redox-active units of one or more of formulae la, lb, Ic, Id, Ie and If as defined above.

[0062] The catholyte comprises as redox-active component a compound of formula II, which is an oligomer or polymer having a plurality of redox-active units of formula I;

[0063]

[0064] In formula II, R1, R2, R3 and R4 have the meanings as defined for formula I, ME is a repeating structural unit derived from a polymerizable monomer, BG is a covalent bond or a bridging group, and r is an integer from 2 to 150, preferably from 2 to 80, and very particularly preferably from 8 to 40.

[0065] The repeating units ME and BG form the backbone of the oligomer or polymer comprising a plurality of redox-active units of formula I as defined above.

[0066] Examples of classes of substances which can form the backbone of the oligomer or polymer are polymers derived from ethylenically unsaturated carboxylic acids or esters or amides thereof, such as polymethacrylates, polyacrylates, polymethacrylamides or polyacrylamides, polymers derived from ethylenically unsaturated aryl compounds, such as polystyrene, polymers derived from vinyl esters of saturated carboxylic acids or derivatives thereof, such as polyvinyl acetate or polyvinyl alcohol, polymers derived from olefins or bicyclic or polycyclic olefins, such as polyethylene, polypropylene or polynorbornene, polyimides derived from tetra-carboxylic acids and diamines which form imides, polymers derived from naturally occurring polymers and chemically modified derivatives thereof, such as cellulose or cellulose ethers, and polyurethanes, polyvinyl ethers, polythiophenes, polyacetylenes, polyalkylene glycols, poly-7-oxanorbornenes, polysiloxanes, polyethylene glycols, and derivatives thereof, such as ethers thereof.

[0067] The following list gives some examples of combinations of structural units ME and bridging groups BG of the above-mentioned classes of substances. Herein are:

[0068]

[0069]

[0070] Particularly preferred classes of substances used to form the backbone of the oligomers or copolymers are polymethacrylates, polyacrylates, polystyrene and polyvinyl ethers. The redox-active units of the formula I are covalently bound to the polymer backbone. The redox-active components containing polymers can exist as linear polymers or they are comb and star polymers, dendrimers, ladder polymers, cyclic polymers, polycatenanes and polyrotaxanes.

[0071] Comb and star polymers, dendrimers, ladder polymers, cyclic polymers, polycatenanes and polyrotaxanes are used. These types are characterized by increased solubility and the viscosity of the obtained solutions is generally lower than for the corresponding linear polymers.

[0072] The solubility of the polymers containing redox-active components used according to the application can additionally be improved by copolymerization or functionalization, for example with polyethylene glycol, polymethacrylic acid, polyacrylic acid or polystyrene sulfonate.

[0073] The preparation of the redox-active oligomeric or polymeric components used according to the application can be carried out using conventional polymerization methods. Examples of this are polymerization in itself, polymerization in solution or emulsion polymerization or suspension polymerization. These procedures are known to the person skilled in the art.

[0074] Examples of the redox-active components of the oligomers or polymers used preferably are oligomers or polymers derived from 1-hydroxy-2,2,6,6-tetramethylpiperidinyl-methacrylate and / or 1-hydroxy-2,2,6,6-tetramethylpiperidinyl-acrylate, in particular copolymeric oligomers or copolymers derived from 1-hydroxy-2,2,6,6-tetramethylpiperidinyl-methacrylate and / or 1-hydroxy-2,2,6,6-tetramethylpiperidinyl-acrylate which are copolymerized for the purpose of improving the solubility with [2-(methacryloyloxy)ethyl]amine or an ammonium salt derived therefrom, such as trimethylammonium chloride, and / or with [2-(acryloyloxy)ethyl]amine or an ammonium salt derived therefrom, such as trimethylammonium chloride.

[0075] When radical R1, R2, R3, R4 and / or R5 one of expression alkyl, then described alkyl both can be branched also can be unbranched.Alkyl typically comprises 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms.The example of alkyl is: methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, amyl group, n-hexyl, n-heptyl, 2-ethylhexyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl or eicosyl.Particularly preferably have the alkyl of 1 to 6 carbon atom.Alkyl can be optionally substituted, for example, by carboxyl or sulfonic acid group, by carboxylate group or sulfonic acid ester group, by carboxylic acid amide group or sulfonic acid amide group, by hydroxyl or amino group or by halogen atom replacement.

[0076] When radical R5 is alkoxy, then described alkoxy can be by both can be branched also can be unbranched alkyl unit composition.Alkoxy typically comprises 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms.The example of alkoxy is: methoxyl group, ethoxy, isopropyloxy, n-butoxy, sec-butoxy, tert-butoxy, pentyloxy, n-hexyloxy, n-heptyloxy, 2-ethylhexyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-tridecyloxy, n-tetradecyloxy, n-pentadecyloxy, n-hexadecyloxy, n-octadecyloxy or eicosyloxy.Particularly preferred is the alkoxy with 1 to 6 carbon atoms.

[0077] When radical R5 represents a haloalkyl group, the haloalkyl group may be either branched or unbranched. A haloalkyl group typically comprises 1 to 20 carbon atoms, which are independently substituted by one or more halogen atoms, preferably 1 to 10 carbon atoms. Examples of halogen atoms are fluorine, chlorine, bromine or iodine. Preferred are fluorine and chlorine. Examples of haloalkyl groups are: trifluoromethyl, difluoromethyl, fluoromethyl, bromodifluoromethyl, 2-chloroethyl, 2-bromoethyl, 1,1-difluoroethyl, 2,2,2-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, 2-chloro-1,1,2-trifluoroethyl, pentafluoroethyl, 3-bromopropyl, 2,2,3,3-tetrafluoropropyl, 1,1,2,3,3,3-hexafluoropropyl, 1,1,1,3,3,3-hexafluoropropyl, 3-bromo-2-methylpropyl, 4-bromobutyl, perfluoropentyl.

[0078] As radical R 1 , R 2 , R 3 , R 4 and / or R 5 one of expression cycloalkyl, then described cycloalkyl is for comprising 3 to 8 that can be substituted independently of one another, the cyclic group of preferred 5,6 or 7 annular carbon atoms typically.The example of substituent is alkyl or can form two alkyls of another ring together with the annular carbon atom that they are connected.The example of cycloalkyl is cyclopropyl, cyclopentyl or cyclohexyl.Cycloalkyl can be randomly substituted, for example, by carboxyl or sulfonic acid group, by carboxylate group or sulfonic acid ester group, by carboxylic acid amide group or sulfonic acid amide group, by hydroxyl or amino group or by halogen atom replacement.

[0079] When radical R5 represents heterocyclic radical, then described heterocyclic radical is typically for having 4 to 10 ring carbon atoms and the cyclic group of at least one ring heteroatom that can be substituted independently of one another.The example of substituent is alkyl or can form two alkyls of another ring together with the ring carbon atoms that they are connected.The example of heteroatoms is oxygen, nitrogen, phosphorus, boron, selenium or sulphur.The example of heterocyclic radical is furyl, thienyl, pyrrole radical or imidazolyl.Heterocyclic radical is preferably aromatic.Heterocyclic radical can be randomly substituted, for example, by carboxyl or sulfonic acid group, by carboxylate group or sulfonic acid ester group, by carboxylic acid amide group or sulfonic acid amide group, by hydroxyl or amino group or by halogen atom replacement.

[0080] When radical R 1 , R 2 , R 3 , R 4 and / or R 5 one of expression aralkyl, then described aralkyl is typically aryl that is covalently bonded to alkyl wherein defined above.Aralkyl can for example be replaced by alkyl or by halogen atom on aromatic ring.An example of aralkyl is benzyl.Aralkyl can be optionally substituted, for example by carboxyl or sulfonic acid group, by carboxylate group or sulfonic acid ester group, by carboxylic acid amide group or sulfonic acid amide group, by hydroxyl or amino group or by halogen atom.

[0081] When the group R5 represents an amino group, the amino group may be unsubstituted or may have 1 or 2 or 3 substituents, preferably alkyl and / or aryl groups. The alkyl substituents may be branched or unbranched. Monoalkylamino or dialkylamino groups typically contain 1 or 2 alkyl groups having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms. Examples of monoalkylamino groups are methylamino, ethylamino, propylamino or butylamino. Examples of dialkylamino groups are diethylamino, dipropylamino or dibutylamino. Examples of trialkylamino groups are triethylamino, tripropylamino or tributylamino.

[0082] When the radical R5 represents halogen, this is understood to mean a covalently bonded fluorine, chlorine, bromine or iodine atom, preferably fluorine or chlorine.

[0083] When R8 represents a divalent to tetravalent organic bridging group, this is understood to be an organic group which is bonded to the remainder of the molecule via 2, 3 or 4 covalent bonds.

[0084] Examples of divalent organic groups are alkylene, alkyleneoxy, poly(alkyleneoxy), alkyleneamino, poly(alkyleneamino), cycloalkylene, arylene, aralkylene or heterocyclylene. These groups have been described in more detail above.

[0085] Alkylene groups can be either branched or unbranched. Alkylene groups typically contain 1 to 20 carbon atoms, preferably 2 to 4 carbon atoms. Examples of alkylene groups are: methylene, ethylene, propylene and butylene. Alkylene groups can optionally be substituted, for example, by carboxyl or sulfonic acid groups, by carboxylate or sulfonic acid ester groups, by carboxylic acid amide or sulfonic acid amide groups, by hydroxyl or amino groups or by halogen atoms.

[0086] Alkyleneoxy and poly(alkyleneoxy) groups may contain both branched and unbranched alkylene groups. The alkylene groups present in an alkyleneoxy or poly(alkyleneoxy) group typically contain 2 to 4 carbon atoms, preferably 2 or 3 carbon atoms. The number of repeating units in a poly(alkyleneoxy) group may vary within a wide range. The typical number of repeating units ranges from 2 to 50. Examples of alkyleneoxy groups are: ethyleneoxy, propyleneoxy, and butyleneoxy. Examples of poly(alkyleneoxy) groups are: poly(ethyleneoxy), poly(propyleneoxy), and poly(butyleneoxy).

[0087] Alkyleneamino and poly(alkyleneamino) groups may contain both branched and unbranched alkylene groups. The alkylene groups present in alkyleneamino or poly(alkyleneamino) groups typically contain 2 to 4 carbon atoms, preferably 2 or 3 carbon atoms. The number of repeating units in a poly(alkyleneamino) group may vary within a wide range. The typical number of repeating units ranges from 2 to 50. Examples of alkyleneamino groups are ethyleneamino, propyleneamino, and butyleneamino groups. Examples of poly(alkyleneamino) groups are poly(ethyleneamino), poly(propyleneamino), and poly(butyleneamino).

[0088] Cycloalkylidene typically comprises 5,6 or 7 ring carbon atoms that can be substituted independently of one another.The example of substituent is alkyl or can form two alkyls of another ring together with the ring carbon atoms that they are connected.An example of cycloalkylidene is cyclohexylene.Cycloalkylidene can be randomly substituted, for example, by carboxyl or sulfonic acid group, by carboxylate group or sulfonic acid ester group, by carboxylic acid amide group or sulfonic acid amide group, by hydroxyl or amino group or by halogen atom replacement.

[0089] Arylene is typically a cyclic aromatic group, and it comprises 5 to 14 carbon atoms that can be substituted independently of one another.The example of arylene is o-phenylene, m-phenylene, p-phenylene, o-biphenylyl, m-biphenylyl, p-biphenylyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl or 9-phenanthryl.Arylene can be randomly substituted, for example, by carboxyl or sulfonic acid group, by carboxylate group or sulfonic acid ester group, by carboxylic acid amide group or sulfonic acid amide group, by hydroxyl or amino group or by halogen atom.The other example of substituent is alkyl or or can form two alkyls of another ring together with the annular carbon atom that they are connected.

[0090] Heterocyclylene is typically a cyclic group comprising 4 to 10 ring carbon atoms and at least one ring heteroatom that can be substituted independently of one another. Examples of heteroatoms are oxygen, nitrogen, phosphorus, boron, selenium or sulphur. Examples of heterocyclylene are furandiyl, thiophenediyl, pyrrolediyl or imidazolediyl. Heterocyclylene is preferably aromatic. Heterocyclylene can be optionally substituted, for example, by carboxyl or sulfonic acid group, by carboxylate group or sulfonic acid ester group, by carboxylic acid amide group or sulfonic acid amide group, by hydroxyl or amino group or by halogen atom. Other examples of substituents are alkyl or or two alkyl groups that can form another ring together with the ring carbon atoms to which they are connected.

[0091] Aralkylene groups are typically aryl groups to which one or two alkyl groups are bonded. Aralkylene groups may be covalently bonded to the remainder of the molecule via their aryl group and their alkyl group or via two alkyl groups. Aralkylene groups may be substituted on the aromatic ring, for example, by alkyl groups or by halogen atoms. Examples of aralkylene groups are benzylene or dimethylphenylene (xylylene).

[0092] Examples of trivalent organic radicals R are alkyltriyl, alkoxytriyl, trimerized (alkyleneoxy), trimerized (alkyleneamino), cycloalkyltriyl, aryltriyl, aralkyltriyl or heterocyclyltriyl. These radicals correspond to the divalent radicals already described in detail above, with the difference that they are bonded to the rest of the molecule with three covalent bonds instead of two.

[0093] Examples of tetravalent organic radicals R are alkyltetrayl, alkoxytetrayl, tetrapoly(alkyleneoxy), tetrapoly(alkyleneamino), cycloalkyltetrayl, aryltetrayl, aralkyltetrayl or heterocyclyltetrayl. These radicals correspond to the divalent radicals already described in detail above, with the difference that they are bonded to the rest of the molecule with four covalent bonds instead of two.

[0094] R6 is a monovalent organic group with a zero-fold positive charge, preferably a single positive charge. In this case, it is usually an alkyl, alkoxy, haloalkyl, cycloalkyl, aryl, aralkyl or heterocyclic group, which contains 1 to 4 positively charged groups, especially quaternary ammonium groups, quaternary phosphonium groups, tertiary sulfonium groups or monovalent heterocyclic groups with a one to four-fold charge. The charge balance is provided by one or more anions X q- The connection of the o-fold positively charged group to the piperidine-1-oxy group is preferably carried out via a heteroatom of the o-fold positively charged group. A particularly preferred example of the group R6 is the group -N + R 11 R 12 R 13 、-P + R 11 R 12 R 13 、-S + R 11 R 12 or –Het + , where R 11 、R 12 and R 13 R is independently hydrogen, alkyl, cycloalkyl, aryl, aralkyl or heterocyclic, in particular C1-C6-alkyl, cyclohexyl, phenyl or benzyl, and Het is a monovalent and singly positively charged heterocyclic group having 1 to 3 ring nitrogen atoms or 1 ring nitrogen atom and 1 to 2 ring oxygen atoms or ring sulfur atoms, particularly preferably a monovalent imidazolium, pyridinium, guanidinium, uronium, thiouronium, piperidinium or morpholinium group.

[0095] R9 is a divalent to tetravalent organic group with m times of positive charge. In this case, it is an organic group with m positive charges and bonded to the rest of the molecule by 2,3 or 4 covalent bonds. The example of R9 corresponds to the example shown in the above text to R8 in addition, and difference is that these groups are replaced by the group with m positive charges in addition or have the group with m positive charges in the molecular skeleton. Therefore, R9 can represent alkylene, alkyleneoxy, poly (alkyleneoxy), alkyleneamino, poly (alkyleneamino), cycloalkylene, arylene, aralkylene or heterocyclic radical, which are replaced by the group with m single times of positive charge. The example of positively charged group is quaternary ammonium, quaternary phosphonium, tertiary sulfonium or divalent to tetravalent heterocyclic group with m times of charge. The group R9 with m times of positive charge is preferably carried out by the heteroatoms of the group with m times of positive charge to the connection of piperidine-1-oxy group. The particularly preferred example of group R9 is group-N + R 14 R 15 -R 16 -[N + R 14 R 15 ] f-、-P + R 14 R 15 -R 16 -[P + R 14 R 15 ] f -、-S + R 14 -R 15 -[S + R 14 ] f -or-[Het m+ ] f -, where R 14 and R 15 are independently of one another alkyl, cycloalkyl, aryl, aralkyl or heterocyclyl, in particular C1-C6-alkyl, cyclohexyl, phenyl or benzyl, f has the meaning defined above, R 16 R represents an f+1 valent organic group and Het represents a divalent to tetravalent heterocyclic group with m times positive charge, which has 1 to 3 ring nitrogen atoms or 1 ring nitrogen atom and 1 to 2 ring oxygen atoms or ring sulfur atoms, and is particularly preferably a divalent to tetravalent imidazolium, pyridinium, guanidinium, uronium, thiouronium, piperidinium or morpholinium group. 16 The instance of corresponds to the instance of R8.

[0096] Divalent organic group R 16 Examples of are alkylene, cycloalkylene, arylene, aralkylene or heterocyclylene. These groups have already been described in detail above.

[0097] trivalent organic group R 16 Examples of are alkyltriyl, cycloalkyltriyl, aryltriyl, aralkyltriyl or heterocyclyltriyl. These groups correspond to the divalent groups already described in detail above, with the difference that they are bonded to the remainder of the molecule with three covalent bonds instead of two.

[0098] tetravalent organic group R 16 Examples are alkyltetrayl, cycloalkyltetrayl, aryltetrayl, aralkyltetrayl or heterocyclyltetrayl. These groups correspond to the divalent groups already described in detail above, with the difference that they are bonded to the remainder of the molecule with four covalent bonds instead of two.

[0099] R7 is a monovalent organic group with a negative charge of one fold, preferably a single negative charge. In this case, it is usually an alkyl, alkoxy, haloalkyl, cycloalkyl, aryl, aralkyl or heterocyclic group, which contains 1 to 4 groups with a negative charge of one fold, especially 1 to 4 carboxylic acid groups or 1 to 4 sulfonic acid groups or a monovalent heterocyclic group substituted by 1 to 4 carboxylic acid groups or by 1 to 4 sulfonic acid groups. The charge balance is provided by one or more cations Z q+ The attachment of the u-fold negatively charged group to the piperidine-1-oxyl group is preferably carried out via a carbon atom of the singly negatively charged group.

[0100] R 10 is an m-fold negatively charged, preferably singly or doubly negatively charged, divalent to tetravalent organic radical. In this case it is an organic radical having m singly negatively charged radicals and being linked to the rest of the molecule via 2, 3 or 4 covalent bonds. 10 The examples correspond to the examples further shown above for R8, with the difference that these groups are additionally substituted by m singly negatively charged groups or have m negatively charged groups in the molecular skeleton. 26 = can represent an alkylene, alkyleneoxy, poly(alkyleneoxy), alkyleneamino, poly(alkyleneamino), cycloalkylene, arylene, aralkylene or heterocyclylene group, which is substituted by m singly negatively charged groups. Examples of singly negatively charged groups are carboxylic acid groups or sulfonic acid groups or monovalent heterocyclic groups substituted by 1 to 4 carboxylic acid groups or by 1 to 4 sulfonic acid groups. The charge balance is provided by one or more cations Z q+ The attachment of the m-fold negatively charged group to the piperidine-1-oxy group is preferably carried out via a carbon atom of the m-fold negatively charged group.

[0101] The redox-active components of the formulae Ib and Ie used according to the invention comprise a counterion X q- They balance the positive charge present in the rest of the molecule. q- It can be inorganic or organic q-valent anion.

[0102] Inorganic anions X q- Examples are halides, such as fluoride, chloride, bromide or iodide, or hydroxide ions or anions of inorganic acids, such as phosphate, hydrogenphosphate, sulfate, hydrogensulfate, nitrate, hexafluorophosphate, tetrafluoroborate, perchlorate, chlorate, hexafluoroantimonate, hexafluoroarsenate, cyanide and mixtures thereof.

[0103] Organic anion X q-Examples of anions are anions of mono- or polycarboxylic acids or mono- or polysulfonic acids, where these acids may be saturated or unsaturated. Examples of anions of organic acids are acetate, formate, trifluoroacetate, trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, butyrate, citrate, fumarate, glutarate, lactate, malate, malonate, oxalate, pyruvate or tartrate and mixtures thereof.

[0104] The redox-active components of the formulae Ic and If used according to the invention have a counterion Z q+ They balance the negative charge present in the rest of the molecule. q+ It can be inorganic or organic q-valent cation.

[0105] Inorganic cation Z q+ Examples of are hydrogen ions or monovalent or polyvalent metal ions. Preference is given to using hydrogen ions or monovalent or divalent metal ions, in particular alkali metal cations or alkaline earth metal cations.

[0106] Organic cation Z q+ Examples of are ammonium, imidazolium, pyridinium, guanidinium, uronium, thiouronium, piperidinium, morpholinium or phosphonium.

[0107] The index q is preferably 1 or 2 and in particular 1. The index f is preferably 1 or 2 and in particular 1. The index l is preferably 1 / 2 or 1 and in particular 1. The index m is preferably 1 or 2 and in particular 1. The index n is preferably 1 / 2, 1 or 2 and in particular 1 / 2 or 1. The index o is preferably 1 or 2 and in particular 1. The index u is preferably 1 or 2, in particular 1. Particular preference is given to using a cathode electrolyte in the redox flow battery according to the invention which comprises a compound of the formula Ia and / or Id as defined above as the redox-active component.

[0108] It is also particularly preferred to use a cathode electrolyte in the redox flow battery according to the invention, which comprises a compound of the formula Ib and / or Ie or formula Ic and / or If as defined above as a redox-active component, wherein X is selected from halide ions, hydroxide ions, phosphate ions, sulfate ions, perchlorate ions, hexafluorophosphate ions or tetrafluoroborate ions, and wherein Z is selected from hydrogen ions, alkali metal cations or alkaline earth metal cations and substituted or unsubstituted ammonium cations.

[0109] It is likewise particularly preferred to use a cathode electrolyte in the redox flow battery according to the invention, which comprises as redox-active component a compound of the formula I, Ia, Ib, Ic, Id, Ie or If as defined above, and mixtures thereof, in which R1, R2, R3 and R4 represent C1-C6-alkyl and preferably ethyl or methyl.

[0110] Very particularly preferred for use in the redox flow battery according to the application is a positive electrolyte which comprises a compound of the formula la as defined above as redox-active component, wherein R5is hydrogen, Ci-C6-alkyl, Ci-C6-alkoxy, Ci-C6-partially fluorinated alkyl or Ci-C6-perfluorinated alkyl, Ci-C6-partially chlorinated alkyl or Ci-C6-perchlorinated alkyl, Ci-C6-fluorochlorinated alkyl, phenyl, benzyl, fluorine, chlorine, hydroxyl, amino or nitro.

[0111] Very particularly preferred for use in the redox flow battery according to the application is also a positive electrolyte which comprises a compound of the formula Id as defined above as redox-active component, wherein R8is alkylene, alkyltriradical, alkyltetra- radical, alkylenedioxy, alkylenetriol, alkylenetetrol, arylene, aryltriradical, aryltetra- radical, heterocyclylene, heterocyclylenetriol or heterocyclylenetetrol, very particularly preferably C2-C6-alkylene such as ethylene or propylene, or C2-C6-alkylenedioxy such as 1,2- dioxoethylene or 1,3-dioxopropylene, or C3-C6-alkylenetriol such as 1,2,3-propanetriol residue or trimethylolpropane residue, or C4-C6-alkylenetetrol such as pentaerythritol residue, or phenylene, phenyltriradical or phenyltetra-radical.

[0112] Since titanium (IV) cations, vanadium (IV) cations, chromium (III) cations, iron (II) cations, zinc (II) cations and mixtures thereof have a high reversibility with the respective corresponding lower valent titanium (III) cations, titanium (II) cations, vanadium (III) cations, vanadium (II) cations, chromium (II) cations, elemental iron (0), elemental zinc (0) and mixtures thereof, for the sake of convenience in writing and describing below, only titanium (IV) cations, vanadium (IV) cations, chromium (III) cations, iron (II) cations, zinc (II) cations and mixtures thereof are described as starting substances, of course the various forms of existence of titanium (III) cations, titanium (II) cations, vanadium (III) cations, vanadium (II) cations, chromium (II) cations, elemental iron (0), elemental zinc (0) and mixtures thereof are also included in the present application.

[0113] The metal salts used as the anolyte in the redox flow battery according to the present invention include the following metal cations: titanium (IV) cations, vanadium (IV) cations, chromium (III) cations, iron (II) cations, zinc (II) cations, and mixtures thereof. The metal cations in the anolyte may function primarily as active materials but may also serve secondarily as, or as part of, a conductivity additive. The titanium (IV) cations, vanadium (IV) cations, chromium (III) cations, iron (II) cations, zinc (II) cations, and mixtures thereof used according to the present invention are preferably water-soluble. The titanium(IV) cation, vanadium(IV) cation, chromium(III) cation, iron(II) cation, zinc(II) cation and mixtures thereof may have any inorganic or organic anion, such as fluoride, chloride, bromide or iodide, or hydroxide ions or anions of inorganic acids, such as phosphate, hydrogenphosphate, sulfate, hydrogensulfate, nitrate, hexafluorophosphate, tetrafluoroborate, perchlorate, chlorate, hexafluoroantimonate, hexafluoroarsenate, cyanide, acetate, formate, trifluoroacetate, trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, butyrate, citrate, fumarate, glutarate, lactate, malate, malonate, oxalate, pyruvate or tartrate and mixtures thereof.

[0114] "Water-soluble" is understood within the scope of this specification as the solubility of at least 1 g of compound in 1 L of water at 25°C.

[0115] Examples of the titanium salts are titanium chloride, titanium fluoride, titanium bromide, titanium iodide, titanium nitrate, titanium nitrite, titanium carbonate, titanium hydrogen carbonate, titanium sulfate, titanium hydrogen sulfate, titanium oxysulfate, titanium phosphate, titanium monohydrogen phosphate, titanium dihydrogen phosphate, titanium perchlorate, titanium thiocyanate salts, hexacyanotitanates, titanium tetrafluoroborate, titanium hexafluorophosphate, fluorotitanates, titanium oxide. In addition to titanium salts with inorganic anions, titanium salts with organic anions, such as titanium acetate, titanium oxalate or titanium formate, can also be used.

[0116] Examples of the vanadium salts are vanadium chloride, vanadium fluoride, vanadium bromide, vanadium iodide, vanadium nitrate, vanadium nitrite, vanadium carbonate, vanadium bicarbonate, vanadium sulfate, vanadium bisulfate, vanadium oxysulfate, vanadium phosphate, vanadium monohydrogen phosphate, vanadium dihydrogen phosphate, vanadium perchlorate, vanadium thiocyanate salts, hexacyanovanadates, vanadium tetrafluoroborate, vanadium hexafluorophosphate, fluorovanadates, vanadium oxide. In addition to vanadium salts with inorganic anions, vanadium salts with organic anions, such as vanadium acetate, vanadium oxalate or vanadium formate, can also be used.

[0117] Examples of chromium salts include chromium chloride, chromium fluoride, chromium bromide, chromium iodide, chromium nitrate, chromium nitrite, chromium bicarbonate, chromium carbonate, chromium sulfate, chromium bisulfate, chromium phosphate, chromium monohydrogen phosphate, chromium dihydrogen phosphate, chromium perchlorate, chromium thiocyanate salts, hexacyanochromates, chromium tetrafluoroborate, chromium hexafluorophosphate, fluorochromates, and chromium oxide. In addition to chromium salts with inorganic anions, chromium salts with organic anions, such as chromium acetate, chromium oxalate, or chromium formate, can also be used.

[0118] Examples of iron salts are ferric chloride, ferric fluoride, ferric bromide, ferric iodide, ferric nitrate, ferric nitrite, ferric carbonate, ferric bicarbonate, ferric sulfate, ferric bisulfate, ferric phosphate, ferric monohydrogen phosphate, ferric dihydrogen phosphate, ferric perchlorate, ferric thiocyanates, hexacyanoferrates, ferric tetrafluoroborate, ferric hexafluorophosphate, fluoroferrates, and ferric oxide. In addition to iron salts with inorganic anions, vanadium salts with organic anions, such as ferric acetate, ferric oxalate, or ferric formate, can also be used.

[0119] Examples of zinc salts are zinc chloride, zinc fluoride, zinc bromide, zinc iodide, zinc nitrate, zinc nitrite, zinc carbonate, zinc bicarbonate, zinc sulfate, zinc bisulfate, zinc phosphate, zinc monohydrogen phosphate, zinc dihydrogen phosphate, zinc perchlorate, zinc thiocyanate, hexacyanozincates, zinc tetrafluoroborate, zinc hexafluorophosphate, fluorozincates, zinc oxide. In addition to zinc salts with inorganic anions, zinc salts with organic anions, such as zinc acetate, iron oxalate or zinc formate, can also be used.

[0120] Particularly preferred redox flow batteries according to the invention have a positive electrode based on a 1-hydroxy-2,2,6,6-tetramethylpiperidinium group, which has the redox couple 1-hydroxy-2,2,6,6-tetramethylpiperidinium group / 1-oxy-2,2,6,6-tetrasubstituted piperidinium group / 1-oxo-2,2,6,6-tetrasubstituted piperidinium group.

[0121] A particularly preferred redox flow battery according to the present invention has a negative electrode of one of titanium ions, vanadium ions, chromium ions, iron ions, zinc ions, or a mixture thereof, and the negative electrode has a redox pair of one of titanium (IV) / titanium (III) / titanium (II), vanadium (IV) / vanadium (III) / vanadium (II), chromium (III) / chromium (II), iron (II) / elemental iron (0), zinc (II) / elemental zinc (0), or a mixed pair thereof.

[0122] The redox-active components are preferably used in dissolved form, but it is also possible to use dispersions of the redox-active components or to use liquid redox-active components.

[0123] The molar mass of the redox-active component containing a group of formula I used in the cathode electrolyte according to the present invention can vary within a wide range. Particular preference is given to using a redox-active component containing a group of formula I, the molar mass of the redox-active substance of the cathode electrolyte fluctuating in the range of 150 to 20,000 g / mol, preferably in the range of 150 to 2,000 g / mol and very particularly preferably in the range of 150 to 800 g / mol.

[0124] The molar mass of the redox-active substances of the negative electrode electrolyte fluctuates in the range from 45 to 2000 g / mol, preferably in the range from 47 to 500 g / mol and very particularly preferably in the range from 115 to 300 g / mol.

[0125] In the redox flow battery according to the invention, selected redox-active components are used in two compartments, which are separated from one another by a semipermeable membrane and are present in dissolved form, liquid form or dispersed form in the compartments.

[0126] Positive and negative electrolytes consist of water or water and an organic solvent with dissolved substances. They are used to balance the charge during charging and discharging of the battery or have a positive impact on the stability and performance parameters of the battery. Substances responsible for charge balance are called conductivity additives, while substances that have a positive impact on stability and performance parameters are called auxiliary additives. Conductivity additives are typically organic or inorganic salts. Furthermore, a distinction is made between cathode electrolytes and anode electrolytes when considering electrolytes. The positive electrode electrolyte contains, in addition to a solvent and / or a conductive additive / auxiliary additive, a redox-active positive electrode material 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group, 1-oxy-2,2,6,6-tetrasubstituted piperidine group, 1-oxo-2,2,6,6-tetrasubstituted piperidinium group and mixtures thereof, in particular 1-hydroxy-2,2,6,6-tetramethylpiperidine group, 1-oxy-2,2,6,6-tetramethylpiperidine group (TEMPO), 1-oxo-2,2,6,6-tetramethylpiperidinium group and mixtures thereof. In addition to the solvent and the conductive additive / auxiliary additive, the negative electrode liquid also contains one of the redox active negative electrode materials titanium (IV) / titanium (III) / titanium (II), vanadium (IV) / vanadium (III) / vanadium (II), chromium (III) / chromium (II), iron (II) / elemental iron (0), zinc (II) / elemental zinc (0) or a mixture thereof; similarly, these metal cations or elements can also be part of the additive. Therefore, the redox-active positive electrode materials 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group, 1-oxy-2,2,6,6-tetrasubstituted piperidine group, 1-oxo-2,2,6,6-tetrasubstituted piperidinium group and their mixtures and the negative electrode materials titanium (IV) / titanium (III) / titanium (II), vanadium (IV) / vanadium (III) / vanadium (II), chromium (III) / chromium (II), iron (II) / elemental iron (0), zinc (II) / elemental zinc (0) or their mixtures can also be included in the positive electrode electrolyte and the negative electrode solution to form a symmetrical battery that is not afraid of permeation.

[0127] Examples of positive and negative electrode electrolyte solvents are water, alcohol (e.g., ethanol), carbonate (e.g., propylene carbonate), nitrile (e.g., acetonitrile), amide (e.g., dimethylformamide, dimethylacetamide), sulfoxide (e.g., dimethyl sulfoxide), ketone (e.g., acetone), lactone (e.g., γ-butyrolactone), lactam (e.g., N-methyl-2-pyrrolidone), nitro compound (e.g., nitromethane), ether (e.g., tetrahydrofuran), chlorinated hydrocarbon (e.g., dichloromethane), carboxylic acid (e.g., formic acid, acetic acid), and mineral acid (e.g., sulfuric acid, hydrogen halide, or hydrohalic acid). Preferred are mixtures of one or more of water, carbonate (e.g., propylene carbonate), and nitrile (e.g., acetonitrile). Particularly preferred is water.

[0128] Examples of conductive additives for positive and negative electrode electrolytes are one or more of salts, acids and bases, whose anions are selected from halide ions (fluoride ions, chloride ions, bromide ions, iodide ions), hydroxide ions, anions of inorganic acids (such as phosphate ions, sulfate ions, nitrate ions, hexafluorophosphate ions, tetrafluoroborate ions, perchlorate ions, chlorate ions, hexafluoroantimonate ions, hexafluoroarsenate ions, cyanide ions) or anions of organic acids (such as acetate ions, formate ions, methanesulfonate ions, trifluoroacetate ions, trifluoromethanesulfonate ions, pentafluoroethanesulfonate ions, nonafluorobutanesulfonate ions, butyrate ions, citrate ions, fumarate ions, glutarate ions, lactate ions, malate ions, malonate ions, oxalate ions, pyruvate ions, tartrate ions). Particularly preferred are chloride and fluoride ions, hydroxide ions, phosphate ions, sulfate ions, perchlorate ions, hexafluorophosphate ions and tetrafluoroborate ions; and cations selected from the group consisting of hydrogen ions (H + ), alkali metal cations or alkaline earth metal cations (e.g., lithium, sodium, potassium, magnesium, calcium), zinc, iron, and substituted or unsubstituted ammonium cations (e.g., tetrabutylammonium, tetramethylammonium, tetraethylammonium), where the substituents may generally be alkyl groups. Hydrogen ions, lithium ions, sodium ions, potassium ions, tetrabutylammonium ions, and mixtures thereof are particularly preferred. In particular, conductive salts, acids, and bases include HCl, H2SO4, HNO3, NaCl, KCl, LiPF6, LiBF4, NaBF4, NaPF6, NaClO4, NaOH, KOH, Na3PO4, K3PO4, Na2SO4, NaSO3CF3, LiSO3CF3, (CH3)4NOH, n-Bu4NOH, (CH3)4NCl, n-Bu4NCl, (CH3)4NBr, n-Bu4NBr, n-Bu4NPF6, n-Bu4NBF4, n-Bu4NClO4, and mixtures thereof, where n-Bu represents an n-butyl group.

[0129] Particularly preferred redox flow batteries according to the invention contain in the electrolyte a conductivity additive containing anions selected from halide ions, hydroxide ions, phosphate ions, sulfate ions, perchlorate ions, hexafluorophosphate ions or tetrafluoroborate ions, in particular the conductivity additive consists of these anions and cations selected from hydrogen ions, alkali metal cations or alkaline earth metal cations and substituted or unsubstituted ammonium cations.

[0130] The auxiliary additive may be a mixture of one or more of a complexing agent, a surfactant, a viscosity modifier, a pesticide, a buffer, a stabilizer, a catalyst, a conductivity additive, an antifreeze agent, a temperature stabilizer and a defoaming agent.

[0131] The complexing agent can be ethylenediamine, urea, sulfamic acid, sulfonamide, EDTA, DPTA, acetylacetone, biuret, N,N-dimethylformamide, hydantoin, sodium dehydroacetate, sulfonic acid diamide, oxalic acid, citric acid, malic acid, formic acid, acetic acid and mixtures thereof.

[0132] The surfactant can be nonionic, anionic, cationic or amphoteric. Particularly preferred are nonionic surfactants (e.g., polyalkylene glycol ethers, fatty alcohol propoxylates, alkyl glucosides, alkyl polyglucosides, octylphenol ethoxylates, nonylphenol ethoxylates, saponins, phospholipids) and mixtures thereof.

[0133] The buffer can be a carbonic acid-bicarbonate buffer, a carbonic acid-silicate buffer, an acetic acid-acetate buffer, a phosphate buffer, an ammonia buffer, a citric acid buffer or a citrate buffer, tris(hydroxymethyl)-aminomethane, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, 4-(2-hydroxyethyl)-piperazine-1-propanesulfonic acid, 2-(N-morpholino)ethanesulfonic acid, barbital-acetate buffer) and mixtures thereof.

[0134] Stabilizers can be silicates, amine compounds such as cyclohexylamine, dodecylamine, hexamethylenediamine, ethylenediamine, thiourea and its derivatives, imidazolines, benzotriazole (BTA), phytic acid, amino acids (such as glutamic acid, histidine), lauryl sulfate and mixtures thereof.

[0135] The catalyst can be a bismuth salt, a lead salt, an indium salt, boric acid and boron salt, a titanium salt, a platinum salt, a gold salt, or a mixture of these substances.

[0136] The redox flow battery according to the present invention comprises a semipermeable membrane. This membrane fulfills the following functions: 1) separating the cathode and cathode compartments; 2) retaining the redox-active components in the cathode and cathode solutions, respectively, thereby retaining the cathode and cathode active materials; and 3) providing permeability for the conductive salt of the electrolyte, which is used for charge balancing, i.e., for the anions and / or cations of the conductive salt or for the charge carriers contained in the electrolyte.

[0137] The membrane can be, in particular, a size-exclusion membrane, such as a dialysis membrane, but can also be an ion-selective membrane. The membrane prevents the interpenetration of redox-active compounds of 1-hydroxy-2,2,6,6-tetrasubstituted-piperidinyl groups, 1-oxy-2,2,6,6-tetrasubstituted-piperidinyl groups, 1-oxo-2,2,6,6-tetrasubstituted-piperidinium groups, and mixtures thereof, and titanium cations, vanadium cations, chromium cations, iron cations, elemental iron, zinc cations, and elemental zinc.

[0138] The membrane used according to the invention, for example an ion-permeable membrane for the conductivity additive or a dialysis membrane, separates the redox-active component in the two compartments.

[0139] Depending on the application, the diaphragm can be made of plastic, ceramic, glass, metal, or textile web. Examples of materials include organic polymers such as cellulose or modified cellulose, for example, cellulose ethers or cellulose esters, polyethersulfone, polysulfone, polyvinylidene fluoride, polyester, polyurethane, polyamide, polypropylene, polyvinyl chloride, polyacrylonitrile, polystyrene, polyvinyl alcohol, polyphenylene ether, polyimide, polytetrafluoroethylene, and its derivatives, as well as ceramic, glass, or felt. Diaphragms composed of multiple materials (composites) are also possible. Ion exchange membranes, both cation exchange membranes and anion exchange membranes, are also possible.

[0140] The thickness of the separator used according to the invention can vary within wide ranges. Typical thicknesses are between 0.1 μm and 5 mm, particularly preferably in the range between 10 μm and 200 μm.

[0141] In addition to the redox-active components, electrolyte, and separator described above, the redox flow battery according to the present invention preferably includes the following additional components: 1) a delivery device, such as a pump, as well as tanks and tubes, for transporting and storing the redox-active components; 2) electrodes, preferably composed of or including graphite, graphite fiber mesh, graphite paper, carbon nanotube blanket, activated carbon, carbon black, or graphene, or carbon felt, the electrode surface of which may be loaded with elements such as titanium, lead, boron, and nitrogen; and 3) an optional current collector, such as aluminum, an aluminum alloy, copper, stainless steel, Hastelloy, an iron-chromium-nickel alloy, precious metal-coated titanium or tantalum, particularly platinum-coated and / or iridium-coated and / or ruthenium oxide-coated titanium, niobium, tantalum, hafnium, or zirconium.

[0142] The low-cost liquid flow battery of the present invention can be widely used in the fields of mobile and fixed energy storage devices: (1) as a fixed energy storage device, suitable for grid-level backup power supply systems, peak-valley load regulation systems, and energy cache units in the coordinated systems of renewable energy power generation (especially photovoltaic and wind power generation) and traditional energy (gas / coal / biomass / tidal / offshore power plants); (2) as a mobile energy storage device integrated into the power systems of electric vehicles, including land-based vehicles, aircraft and ships.

[0143] Redox flow batteries incorporating the low-cost flow batteries of the present invention offer significant advantages in miniaturized applications, particularly in home energy storage systems and mobile devices. This is because they offer high power and capacity, low power consumption, low toxicity, uncomplicated construction, and low operating costs in a smaller package than conventional redox flow batteries.

[0144] The application will be further described in connection with the following examples.

[0145] Example 1

[0146] This example discloses a low-cost flow battery, the positive electrolyte uses chlorinated (1-oxyl-2, 2, 6, 6-tetramethylpiperidin-4-yl) trimethylammonium as the positive active material, dissolved in water, the concentration is 1.5mol / L; uses chromium chloride as the negative active material, dissolved in water, the concentration is 2.0mol / L; the ion membrane is an anion membrane, and the electrode material is carbon felt. Figure 1 The test device is shown in the following figure.

[0147] The positive electrode charging and discharging reaction formula is:

[0148]

[0149] The negative electrode charging and discharging reaction formula is:

[0150]

[0151] The charging and discharging curve of the low-cost flow battery is shown in the following figure. Figure 2 It can be seen that chlorinated (1-oxyl-2, 2, 6, 6-tetramethylpiperidin-4-yl) trimethylammonium is paired with chromium chloride, has the charging and discharging capacity, avoids the use of rare metals, and reduces the initial installation cost of the flow battery.

[0152] Example 2

[0153] This example discloses a low-cost flow battery, the positive electrolyte uses chlorinated (1-oxyl-2, 2, 6, 6-tetramethylpiperidin-4-yl) trimethylammonium as the positive active material, dissolved in water, the concentration is 1.5mol / L, and 2.0mol / L HCl is further added in the positive electrolyte, and the total amount is 50ml; uses chromium chloride as the negative active material, dissolved in water, the concentration is 2.0mol / L, and 2.0mol / L HCl and 0.005mol / L PbCl2 are further added in the negative electrolyte, and the total amount is 50ml; the ion membrane is an anion membrane, and the electrode material is carbon felt. Figures 3-6 The charging and discharging curve, coulombic efficiency, energy efficiency and discharge capacity of the low-cost flow battery can be seen, and by adding the supporting electrolyte HCl and the catalyst lead chloride, the stability is significantly increased compared with example 1, the energy efficiency is stably above 80%, and the capacity utilization rate is about 74.6%.

[0154] Example 3

[0155] The embodiment discloses a low-cost liquid flow battery, a positive electrolyte takes chlorinated (1-hydroxy-2, 2, 6, 6-tetramethylpiperidin-4-yl) trimethylammonium as a positive active material, is dissolved in water, and the concentration is 1.5mol / L, 2.0mol / L HCl is continuously added in the positive electrolyte, and the total amount is 50ml; chromium trichloride is used as a negative active material, is dissolved in water, and the concentration is 2.0mol / L, 2.0mol / L HCl and 0.005mol / L PbCl2 are continuously added in the negative electrolyte, and the total amount is 90ml; an ion membrane is a negative ion membrane, and an electrode material is carbon felt.

[0156] The positive electrode charging and discharging reaction formula is:

[0157]

[0158] The negative electrode charging and discharging reaction formula is:

[0159]

[0160] Figures 7-10 For the charging and discharging curve, coulombic efficiency, energy efficiency and discharge capacity of the low-cost liquid flow battery, it can be seen that the two electrons do not have a significant second-order platform when used, which shows that the system will not significantly reduce the battery energy efficiency when the two electrons are used; the discharged capacity is twice that of the embodiment 2 with the same positive electrolyte and concentration, the capacity utilization rate of the two electrons is more than 75%, which proves the feasibility of the two-electron use of the system, and also proves the superior energy density and cost advantage of the system.

Claims

1. A low-cost flow battery, characterized in that: The redox active substance of the positive electrode electrolyte contains a hydroxylamine ring structure group having a hindered amine; The redox active material of the positive electrode electrolyte contains the structure of formula Y: ； In formula Y, the cyclic structure is a 3-membered ring, a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring, or an 8-membered ring; the cyclic structure contains one or more of a carbon-carbon single bond, a carbon-carbon double bond, and a carbon-carbon triple bond; R1, R2, R3, and R4 are independently selected from alkyl, cycloalkyl, aryl, and aralkyl groups.

2. The low-cost flow battery according to claim 1, characterized in that: The redox active material of the positive electrode electrolyte contains one or more of a 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group, a 1-hydroxy-2,2,5,5-tetrasubstituted pyrrole group and a 1-hydroxy-2,2,5,5-tetrasubstituted pyrroline group.

3. The low-cost flow battery according to claim 1, characterized in that: The redox active material of the positive electrode electrolyte contains one or more of a 1-hydroxy-2,2,6,6-tetrasubstituted piperidine group, a 1-oxy-2,2,6,6-tetrasubstituted piperidine group and a 1-oxo-2,2,6,6-tetrasubstituted piperidinium group.

4. The low-cost flow battery according to claim 1, characterized in that: The positive electrode electrolyte contains a compound containing at least one group of formula I as a redox active component: ； Wherein, the line leaving position 4 in the structure of Formula I represents a covalent bond, and the structure of Formula I is connected to the rest of the compound molecule through a covalent bond at position 4, and R1, R2, R3 and R4 are independently selected from alkyl, cycloalkyl, aryl and aralkyl.

5. The low-cost liquid flow battery according to claim 1 or 2, characterized in that: The positive electrode electrolyte comprises a compound having one or more of Formulas Ia, Ib, Ic, Id, Ie and If as a redox active component: ； ； ； In Formulas Ia, Ib, Ic, Id, Ie, and If, R1, R2, R3, and R4 are independently selected from alkyl, cycloalkyl, aryl, and aralkyl groups; X represents a q-valent inorganic or organic anion or a mixture of such anions, q being an integer from 1 to 3, o being an integer from 1 to 4, and u being an integer from 1 to 4; R8 is a divalent to tetravalent organic bridging group; R5 is hydrogen, alkyl, alkoxy, haloalkyl, cycloalkyl, aryl, aralkyl, heterocyclyl, halogen, hydroxy, amino, nitro or cyano; R6 is a monovalent organic group with a single positive charge, or a monovalent heterocyclic group with a single positive charge; R9 is a divalent to tetravalent organic group with an m-fold positive charge, or a divalent to tetravalent heterocyclic group with an m-fold positive charge; R7 is a monovalent group with a single negative charge, or a monovalent heterocyclic group with a single negative charge; R 10 It is a divalent to tetravalent organic group with m times negative charge; Z is a q-valent inorganic or organic cation or a mixture of cations of this type, f is an integer from 1 to 3, l is a number having the value o / q or u / q, m is an integer from 1 to 4, and n represents a number having the value m / q.

6. The low-cost flow battery according to claim 5, characterized in that: The R6 is a quaternary ammonium group, a quaternary phosphonium group or a tertiary sulfonium group.

7. The low-cost flow battery according to claim 5, characterized in that: The R9 is a divalent to tetravalent quaternary ammonium group, a divalent to tetravalent quaternary phosphonium group, or a divalent to trivalent tertiary sulfonium group.

8. The low-cost flow battery according to claim 5, characterized in that: The R7 is a carboxyl group or a sulfonic acid group.

9. The low-cost flow battery according to claim 5, characterized in that: The R 10 It is an alkylene group substituted by 1 or 2 carboxyl groups or sulfonic acid groups, or a phenylene group substituted by 1 or 2 carboxyl groups or sulfonic acid groups, or a divalent heterocyclic group substituted by 1 or 2 carboxyl groups or sulfonic acid groups.

10. The low-cost flow battery according to claim 1, characterized in that: The positive electrode electrolyte comprises a compound of formula II as a redox active component: ； In formula II, R1, R2, R3 and R4 are independently selected from alkyl, cycloalkyl, aryl and aralkyl groups, ME is a repeating structural unit derived from a polymerizable monomer, BG is a covalent bond or a bridging group, and r is an integer from 2 to 150.

11. The low-cost flow battery according to claim 1, characterized in that: The redox active material of the negative electrode electrolyte contains one or more of titanium, vanadium, chromium, iron and zinc.

12. The low-cost flow battery according to claim 11, characterized in that: The redox active substance of the positive electrode electrolyte has a molar mass of 150 to 20,000 g / mol; And / or, the molar mass of the redox active substance of the negative electrode electrolyte is 45 to 2000 g / mol.

13. Application of the low-cost liquid flow battery according to any one of claims 1 to 12 in the field of mobile and fixed energy storage.

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