Fluoropiperidine nitroxide radical derivatives and their applications in positive electrode electrolytes.

Abstract

This invention discloses a fluoropiperidine nitroxide radical derivative, a positive electrode electrolyte containing the same, and its applications. The fluoropiperidine nitroxide radical derivative is a compound represented by Formula I. The piperidine nitroxide radical derivative of this invention exhibits high stability and high solubility as a positive electrode active material in organic flow batteries, showing promising application prospects.

Description

Technical Field

[0001] This invention relates to a fluoropiperidine nitric oxide radical derivative, a positive electrode electrolyte containing the same, and its applications. Background Technology

[0002] Flow batteries are widely used in wind power, photovoltaic power, energy storage, and grid peak shaving and frequency regulation. Their key feature is that rated energy and rated power are independent. Rated energy depends on the amount of active material in the electrolyte in the storage tank, while power depends on the active area of ​​each electrode in the stack and the number of electrodes. Both can be independently expanded, easily adapting to different application scenarios and achieving efficient long-term cycling. Furthermore, aqueous flow batteries using organic redox active materials have advantages such as high ionic conductivity, abundant raw materials, good controllability, and safety and environmental friendliness, showing great development potential. However, currently, organic flow batteries are limited by the poor solubility and stability of redox active materials, making it difficult to meet the ever-increasing demands for long lifespan, high safety, low cost, and high energy density in practical applications.

[0003] Studies have shown that the decomposition or irreversible oxidation of redox active materials is one of the main causes of cycle capacity decay in organic flow batteries. Therefore, improving the chemical and electrochemical stability of active materials to ensure that they undergo stable reversible redox reactions during battery operation, thereby improving the cycle life of flow batteries, has become one of the main research directions.

[0004] The energy density, cycle life, and power performance of organic flow batteries largely depend on the solubility, stability, redox reversibility, and electrochemical kinetics of the redox active materials.

[0005] Therefore, the search for highly stable active materials has become a current research hotspot. Summary of the Invention

[0006] The technical problem this invention aims to solve is to overcome the instability of positive electrode active materials in existing organic flow batteries, which leads to poor battery cycle stability. To address this, this invention provides a fluoropiperidine nitroxide radical derivative, a positive electrode electrolyte containing the derivative, and its applications. The piperidine nitroxide radical derivative of this invention exhibits high stability and high solubility as a positive electrode active material in organic flow batteries, thereby significantly improving the energy density, rate performance, and cycle life of organic flow batteries, effectively reducing commercial costs, and enhancing practical value.

[0007] The present invention solves the above-mentioned technical problems through the following solution.

[0008] This invention provides a compound as shown in Formula I:

[0009]

[0010] It is defined as group 1, group 2, or group 3 as follows:

[0011] Group 1:

[0012] R 1 H, hydroxyl, Cl, Br, I, Cl-C 20 Alkyl groups, C1-C substituted with one or more Cl atoms 20 Alkyl groups, C1-C substituted with one or more Br radicals 20 Alkyl groups, C1-C substituted with one or more I groups 20 Alkyl, C1-C 20 The alkoxy group, substituted with one or more Cl atoms, is a C1-C group. 20 The alkoxy group, substituted with one or more Br atoms at C1-C 20 The alkoxy group, substituted with one or more I atoms at C1-C 20 alkoxy groups, C1-C 20 heteroalkyl groups, C1-C substituted with one or more Cl atoms 20 heteroalkyl groups, C1-C substituted with one or more Br atoms 20 heteroalkyl groups, or C1-C groups substituted with one or more I groups. 20 heteroalkyl groups;

[0013] X is a C1-C molecule replaced by one or more F molecules. 20 Alkylene, C1-C substituted with one or more F atoms 20 The alkene oxide, or the C1-C substituted with one or more Fs. 20 heteroalkyl groups;

[0014] R 2 H, -COOY a2 -SO2OY b2 or -PO(OY c2 )2;

[0015] Y a2 Y b2 and Y c2 Independently classified as H, alkali metals, alkaline earth metals, transition metals, -N(R) 7 R 8 R 9 ) or -P(R 10 R 11 R 12 );

[0016] R 3 R 4 R 5 R 6R 7 R 8 R 9 R 10 R 11 and R 12 Alkyl groups that are independently C1-C6;

[0017] Group 2:

[0018] R 1 F, C1-C replaced by one or more F 20 Alkyl groups, C1-C substituted with one or more F groups 20 The alkoxy group or C1-C substituted with one or more F groups 20 heteroalkyl groups;

[0019] X does not exist, C1-C 20 Alkylene, C1-C substituted with one or more F 20 Alkylene, C1-C substituted with one or more Cl atoms 20 Alkylene, C1-C substituted with one or more Br 20 Alkylene, C1-C substituted with one or more I groups 20 Alkylene, C1-C 20 The alkene oxide, C1-C substituted with one or more F atoms. 20 The alkene group, C1-C substituted with one or more Cl atoms. 20 The alkene oxide, C1-C substituted with one or more Br atoms. 20 The alkene oxide, C1-C substituted with one or more I atoms. 20 alkeneoxy group, C1-C 20 Heteroalkyl groups, C1-C substituted with one or more F groups 20 Heteroalkyl groups, C1-C substituted with one or more Cl atoms 20 Heteroalkyl groups, C1-C substituted with one or more Br atoms 20 Heteroalkyl groups or C1-C groups substituted with one or more I atoms 20 heteroalkyl groups;

[0020] R 2 -COOY a2 -SO2OY b2 or -PO(OY c2 )2;

[0021] Y a2 Y b2 and Y c2 Independently classified as H, alkali metals, alkaline earth metals, transition metals, -N(R) 7 R 8 R 9) or -P(R 10 R 11 R 12 );

[0022] R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 R 11 and R 12 Alkyl groups that are independently C1-C6;

[0023] Group 3:

[0024] R 1 -COOY a1 -SO2OY b1 or -PO(OY c1 )2;

[0025] X is a C1-C molecule replaced by one or more F molecules. 20 Alkylene, C1-C substituted with one or more F atoms 20 The alkene oxide or C1-C substituted with one or more F atoms 20 heteroalkyl groups;

[0026] R 2 H, halogen, -COOY a2 -SO2OY b2 or -PO(OY c2 )2;

[0027] Y a1 Y b1 Y c1 Y a2 Y b2 and Y c2 Independently classified as H, alkali metals, alkaline earth metals, transition metals, -N(R) 7 R 8 R 9 ) or -P(R 10 R 11 R 12 );

[0028] R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 R 11 and R12 Alkyl groups that are independently C1-C6;

[0029] In groups 1, 2, and 3, the C1-C 20 heteroalkyl groups, C1-C groups substituted with one or more F atoms 20 Alkylene, C1-C substituted with one or more Cl atoms 20 heteroalkyl groups, and C1-C groups substituted with one or more Br. 20 heteroalkyl groups, and C1-C groups substituted with one or more I atoms. 20 heteroalkyl groups, the C1-C 20 Heteroalkyl groups, C1-C groups substituted with one or more F atoms 20 Heteroalkyl groups, C1-C groups substituted with one or more Cl atoms 20 Heteroalkyl groups, C1-C groups substituted with one or more Br 20 Heteroalkyl groups and C1-C groups substituted with one or more I atoms 20 The heteroatoms in the heteroalkylene group are independently one or more of S, O, N, Si, P and B, and the number is 1, 2, 3, 4 or 5.

[0030] In a particular embodiment, certain technical features have the following meanings, while the meanings of other technical features are as described in any of the preceding embodiments (hereinafter referred to as "in a particular embodiment"):

[0031] In one particular scheme, R 1 In the context, C1-C 20 Alkyl groups, C1-C groups substituted with one or more F groups 20 Alkyl groups, C1-C groups substituted with one or more Cl atoms 20 Alkyl groups, C1-C groups substituted with one or more Br 20 alkyl groups and C1-C groups substituted with one or more I groups 20 C1-C in alkyl groups 20 The alkyl group is independently a C1-C6 alkyl group.

[0032] In one particular scheme, R 1 In the context, C1-C 20 The alkoxy group, the C1-C group substituted with one or more F groups. 20 The alkoxy group, the C1-C group substituted with one or more Cl atoms 20 The alkoxy group, the C1-C group substituted with one or more Br atoms 20 The alkoxy group and the C1-C group substituted with one or more I groups. 20 C1-C in alkoxy groups 20The alkoxy group is independently a C1-C6 alkoxy group.

[0033] In one particular scheme, R 1 In the context, C1-C 20 heteroalkyl groups, C1-C groups substituted with one or more F atoms 20 heteroalkyl groups, and C1-C groups substituted with one or more Cl atoms. 20 heteroalkyl groups, and C1-C groups substituted with one or more Br. 20 heteroalkyl groups and C1-C groups substituted with one or more I atoms 20 C1-C in heteroalkyl groups 20 The heteroalkyl groups are independently C1-C6 heteroalkyl groups.

[0034] In one scheme, in X, the C1-C 20 Alkylene, C1-C substituted with one or more F 20 Alkylene, C1-C substituted with one or more Cl atoms 20 Alkylene, C1-C substituted with one or more Br 20 alkylene groups and C1-C groups substituted with one or more I atoms 20 C1-C in alkylene 20 The alkylene group is independently a C1-C6 alkylene group, and can be methylene, etc. For example, methylene.

[0035] In one scheme, in X, the C1-C that is replaced by one or more F... 20 Alkylene, C1-C substituted with one or more Cl atoms 20 Alkylene, C1-C substituted with one or more Br 20 alkylene groups and C1-C groups substituted with one or more I atoms 20 The plurality of alkylene groups are independently 2, 3 or 4, for example 2.

[0036] In one scheme, in X, the C1-C that is replaced by one or more F... 20 The alkylene group is -CF2-.

[0037] In one scheme, in X, the C1-C 20 The alkeneoxy group, the C1-C group substituted with one or more F atoms 20 The alkeneoxy group, the C1-C group substituted with one or more Cl atoms 20 The alkeneoxy group, the C1-C group substituted with one or more Br atoms 20The alkeneoxy group and the C1-C group substituted with one or more I groups 20 C1-C in alkeneoxy 20 The alkene oxides are independently C1-C6 alkene oxides.

[0038] In one scheme, in X, the C1-C 20 Heteroalkyl groups, C1-C groups substituted with one or more F atoms 20 Heteroalkyl groups, C1-C groups substituted with one or more Cl atoms 20 Heteroalkyl groups, C1-C groups substituted with one or more Br 20 Heteroalkyl groups and C1-C groups substituted with one or more I atoms 20 C1-C in heteroalkylene 20 The heteroalkyl groups are independently C1-C6 heteroalkyl groups.

[0039] In one particular scheme, R 2 In this context, the halogen is F, Cl, Br, or I, for example, F.

[0040] In one of the schemes, Y a1 Y b1 Y c1 Y a2 Y b2 and Y c2 In this context, the alkali metal is Li, Na, K, Rb, or Cs, for example, Na.

[0041] In one of the schemes, Y a1 Y b1 Y c1 Y a2 Y b2 and Y c2 In this context, the alkaline earth metal is Mg or Ca.

[0042] In one of the schemes, Y a1 Y b1 Y c1 Y a2 Y b2 and Y c2 In this context, the transition metal is Zn, In, Fe, Ni, Co, or Mn.

[0043] In one particular scheme, R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 R 11 and R12 In this context, the C1-C6 alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl.

[0044] In one particular scheme, R 1 It is a hydroxyl group.

[0045] In a certain scheme, X is C1-C replaced by one or more F. 20 Alkylenes (e.g., -CF2-).

[0046] In one particular scheme, R 1 It is a hydroxyl group;

[0047] X is a C1-C molecule replaced by one or more F molecules. 20 Alkylene;

[0048] R 2 H, -COOY a2 -SO2OY b2 or -PO(OY c2 )2;

[0049] Y a2 Y b2 and Y c2 It is an alkali metal on its own.

[0050] In one particular scheme, R 1 It is a hydroxyl group;

[0051] X is a C1-C molecule replaced by one or more F molecules. 20 Alkylene;

[0052] R 2 -COOY a2 ;

[0053] Y a2 It is an alkali metal.

[0054] In one embodiment, the compound represented by Formula I is any of the following compounds:

[0055]

[0056] The present invention also provides a method for preparing the compound shown in Formula I above, comprising the following steps: under the action of an alkaline reagent, compound II is hydrolyzed in a solvent to obtain compound I as shown below;

[0057]

[0058] R 12 -COOR 13a -SO2OR 13bor -PO(OR) 13c )2;

[0059] R 13a R 14b and R 15c Alkyl groups that are independently C1-C6 (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl);

[0060] R 1 R 3 R 4 R 5 and R 6 The definitions are the same as those described above.

[0061] The conditions and procedures for the hydrolysis reaction can be those conventional in the art, but the present invention preferably includes the following conditions and procedures:

[0062] The alkaline reagent can be an alkali metal base, an alkaline earth metal base, or a transition metal base (e.g., Zn(OH)2). The alkali metal base can be LiOH, NaOH, KOH, or CsOH.

[0063] The solvent may be a mixture of ether solvent and water (e.g., a volume ratio of ether solvent to water of 5:1-30:1, such as 10:1). The ether solvent may be tetrahydrofuran.

[0064] The hydrolysis reaction can be performed at room temperature.

[0065] The progress of the hydrolysis reaction can be monitored using conventional methods in the art (e.g., TLC, HPLC), and the reaction endpoint is generally defined as the absence or disappearance of compound II. The hydrolysis reaction can take 8-24 hours, for example, 12 hours.

[0066] After the hydrolysis reaction is completed, the post-treatment steps are preferably as follows: washing (e.g., washing with dichloromethane) and concentration.

[0067] The present invention also provides a positive electrode electrolyte comprising the compound shown in Formula I, a supporting electrolyte, and a solvent.

[0068] In one embodiment, the concentration of the compound represented by Formula I can be 0.1 mol / L to 3 mol / L, or 0.2 mol / L to 2 mol / L, or for example, 0.2 mol·L⁻¹. -1 .

[0069] In one embodiment, the supporting electrolyte may be one or more of KCl, KOH, KClO4, KOCH3, NaCl, NaOH, NaOAc, NaNO3, Na2SO4, NaClO4, NaOCH3, NaBF4, LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiB(CO2CO2)2, LiBF2(CO2CO2), LiCl, LiN(SO2CF2CF3)2, LiN(SO2CF3)2, LiN(SO2F)2, ZnCl2, NH4Cl, and R4NX, for example, NH4Cl.

[0070] In one embodiment, the concentration of the supporting electrolyte can be 0.5 mol / L to 4 mol / L, for example, 2 mol·L⁻¹. -1 .

[0071] In one embodiment, the solvent may be water (e.g., deionized water) and / or an organic solvent.

[0072] The organic solvent mentioned can be a conventional organic solvent used in electrolytes in the battery field (especially in the field of flow batteries), such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (γ-BL), γ-valerolactone (γ-VL), 1,2-butylene carbonate, 2,3-butanediol carbonate (2,3-BC), 1,2-butanediol carbonate (1,2-BC), 1,2-pentanediol carbonate (PIC), 2-methyl-1,2-butanediol carbonate (i-BC), ethylene methyl carbonate, methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), methyl n-butyl carbonate (n-BMC), methyl isobutyl carbonate (i-BMC), etc. MC), 2-Butylmethyl carbonate (s-BMC), methyl isopropyl carbonate, butenyl carbonate, dibutyl carbonate (DBC), methyl butyl carbonate, fluoroethylene carbonate (FEC), 2,2,2-trifluoroethyl methyl carbonate (MTFEC), 2,2,2-trifluoroethyl ethyl carbonate (ETFEC), 2,2,2-trifluoroethyl propyl carbonate (PTFEC), 2,2,2,2',2',2'-hexafluoroisopropyl methyl carbonate (MHFPC), 2,2,2,2',2',2'-hexafluoroisopropyl ethyl carbonate (EHFPC), bis(2,2,2-trifluoroethyl) carbonate (DTFEC), bis(2,2,3,3-tetrafluoropropyl) carbonate, bis(2,2,3,3,3-pentafluoroethyl) carbonate, bis(2,2,3,3,3-pentafluoroethyl) carbonate, bis(2,2,2-tri ...2-trifluoroethyl) carbonate, bis(2,2,3,3,3-pentafluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate 1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoropropyl carbonate, 1,1,2,2,2-pentafluoroethyl-2,2,3,3,3-pentafluoropropyl carbonate, 4-(2,2,3,3)-tetrafluoropropoxymethyl-[1,3]-dioxolane-2-one, 4-(2,3,3,3)-tetrafluoro-2-trifluoromethyl-propyl-[1,3]-dioxolane-2-one, methyl formate (MF), ethyl acetate (EA), methyl propionate (MP), ethyl propionate (EP), methyl butyrate (MB), ethyl butyrate (EB), methyl acetate (MA), cyclobutyrate (γBL), cyclopentanoate (γVL), N-methylpyrrolidone (NMP), N-methyloxazolidinone (... NMO), methyl difluoroacetate, methyl trifluoroacetate, ethyl trifluoroacetate, formamide, N-methylacetamide, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), 2,2,2-trifluoro-N,N-dimethylacetamide (TFECm), 1,1,-trifluoromethyl-N,N-dimethylformamide (HFPCm), methanol (MT), ethanol (EA), 1-propanol, 2-propanol (IPA), dimethylformaldehyde (DMM), ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether (DEE), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), dimethoxymethane, anisole, 1,4-dioxane, 1,3-dioxolane (1,3-DL), 2-methyl-1,3-dioxolane (2-Me-1,3-DL), 4-methyl-1,3-dioxolane (4-Me-1,3-DL), diglycerides, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, methyl nonafluorobutyl ether, acetone, acetylacetone, n-hexane, toluene, nitromethane, nitrobenzene, 1,2-dichloroethane, acetonitrile (AN), methoxyacetonitrile, propionitrile, butyronitrile, isobutyronitrile, benzonitrile, 3-methoxypropionitrile (MPN), 3-ethoxypropionitrile (EPN), 3-(2,2,2-trifluoroethoxy)propionitrile (EPN) The following are some of the following: malononitrile (MAN), succinic anionyl nitrile (SCN), glutaronitrile (GLN), adiponitrile (ADN), heptanonitrile (PMN), octanoic anionyl nitrile (SUN), azelonium (AZN), sebacate (SEN), dimethyl methylphosphonate (DMMP), dimethyl (2-methoxyethoxy)methylphosphonate (DMMEMP), diethyl (2-methoxyethoxy)methylphosphonate (DEMEMP), dimethyl sulfoxide (DMSO), methyl ethyl sulfone, sulfolane, dibutyl sulfone, ethyl vinyl sulfone, methyl isopropyl sulfone, ethyl isopropyl sulfone, ethyl isobutyl sulfone, isopropyl isobutyl sulfone, 2-butyl isopropyl sulfone, n-butyl isobutyl sulfone, and 2-methoxyethyl methyl sulfone.

[0073] In one embodiment, the positive electrode electrolyte is composed of the compound shown in Formula I, the supporting electrolyte, and the solvent.

[0074] In one embodiment, the positive electrode electrolyte is composed of... (e.g., 0.2 mol·L) -1 ), ammonium chloride (e.g., 2.0 mol·L⁻¹) -1 It is composed of ) and water.

[0075] The present invention also provides an application of the above-described compound as shown in Formula I as a positive electrode active material.

[0076] The present invention also provides the application of the above-described compound, as shown in Formula I, in a flow battery.

[0077] In one embodiment, the flow battery includes the aforementioned positive electrolyte, negative electrolyte, electrode, bipolar plate, flow guide plate, and separator.

[0078] In one embodiment, the negative electrode electrolyte comprises a negative electrode active material, a supporting electrolyte, and a solvent (e.g., water).

[0079] The negative electrode active material can be ZnCl2.

[0080] The molar concentration of the negative electrode active material can be the conventional molar concentration in electrolytes in the battery field (especially in the field of flow batteries), for example, 0.05mol / L-2mol / L, or 0.2mol / L-1.5mol / L, or 0.4mol / L.

[0081] The supporting electrolyte can be a conventional electrolyte in the field of flow batteries, such as one or more of KCl, KOH, KClO4, KOCH3, NaCl, NaOH, NaOAc, NaNO3, Na2SO4, NaClO4, NaOCH3, NaBF4, LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiB(CO2CO2)2, LiBF2(CO2CO2), LiCl, LiN(SO2CF2CF3)2, LiN(SO2CF3)2, LiN(SO2F)2, ZnCl2, NH4Cl, and R4NX, for example, NH4Cl.

[0082] The molar concentration of the supporting electrolyte can be a conventional molar concentration in electrolytes used in flow batteries, such as 0.5 mol / L-4 mol / L, or 1.0 mol / L-2 mol / L, or 1.5 mol / L.

[0083] In one embodiment, the negative electrode electrolyte is composed of zinc chloride, ammonium chloride, and water.

[0084] In one embodiment, the electrode may be a porous electrode or a metal mesh, such as graphite felt.

[0085] In one embodiment, the bipolar plate may be a graphite bipolar plate.

[0086] In one embodiment, the flow guide plate has a cavity for placing the electrode, and an inlet and an outlet connected to the cavity. When the electrode is placed in the cavity of the flow guide plate, one side of the electrode contacts the bipolar plate, and the other side of the electrode contacts the diaphragm. The electrodes are preferably positive electrode graphite felt (e.g., positive electrode graphite felt with dimensions of 25mm*25mm*7mm) and negative electrode graphite felt (e.g., negative electrode graphite felt with dimensions of 25mm*25mm*4mm).

[0087] In one embodiment, the membrane may be an ion exchange membrane or a porous membrane, such as a cation exchange membrane.

[0088] In one embodiment, the flow battery may further include a pump, a clamp, a reservoir, and a current collector.

[0089] The pump described can be a conventional pump in the battery field (especially in the field of flow batteries), such as a peristaltic pump.

[0090] The clamp may consist of a clamping plate, bolts, and an insulating plate.

[0091] The current collector can be a conventional current collector used in the battery field (especially in the field of flow batteries), such as a copper plate.

[0092] In one embodiment, in the flow battery, the positive electrode electrolyte is composed of... It is composed of ammonium chloride and water; the negative electrode electrolyte is composed of zinc chloride, ammonium chloride and water.

[0093] The present invention also provides a compound as shown in Formula II:

[0094]

[0095] Among them, R 1 R 3 R 4 R 5 R 6 and R 12 The definitions are the same as those described above.

[0096] The compound represented by Formula II is any one of the following compounds:

[0097]

[0098] In this invention, "alkyl" refers to a straight-chain or branched alkyl group having a specified number of carbon atoms (e.g., C1-C8). Alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, isobutyl, sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, etc.

[0099] In this invention, "alkylene" refers to a subunit of a saturated straight-chain or branched hydrocarbon formed by the formal elimination of two monovalent or one divalent atom or group. The two valences can be on the same carbon atom or on different carbon atoms (e.g., the two valences are on the carbon atoms at opposite ends). For example, methylene can be (-CH2-), and ethylene can be -CH2CH2- or -CH(CH3)-. "alkylene" is, for example, a C1-C4 alkylene, such as methylene, etc.

[0100] In this invention, "alkoxy" refers to the group R X -O-, where R X It is an alkyl group as defined above.

[0101] In this invention, "alkoxide" refers to the group -R X -O-, where -R X - refers to the alkylene group defined above.

[0102] In this invention, "heteroalkyl" (e.g., C1-C) 10 Heteroalkyl generally refers to one or more (e.g., 2, 3, 4 or 5, etc.) of an alkyl group (which may be branched or straight-chain alkyl) whose -CH2- is replaced by one or more heteroatoms (which may be one or more of S, O, N, Si, P and B), and the heteroalkyl group is attached to other groups with a carbon atom.

[0103] In this invention, "heteroalkylene" generally refers to one or more (e.g., 2, 3, 4 or 5, etc.) of an alkylene group (which may be branched or straight-chain) whose -CH2- is replaced by one or more heteroatoms (which may be one or more of S, O, N, Si, P and B), and the heteroalkylene group is connected to other groups with a carbon atom.

[0104] In this invention, "multiple" refers to 2, 3, 4, 5, 6, 7, 8, 9, or 10.

[0105] Generally, the term "substituted" indicates that one or more hydrogen atoms in a given structure are substituted by a specific substituent. Further, when the group is substituted by more than one of the substituents, the substituents are independent of each other; that is, the more than one substituent can be different or the same. Unless otherwise indicated, a substituent can be substituted at each substituted position of the substituted group. When more than one position in a given structural formula can be substituted by one or more substituents selected from a specific group, the substituents can be substituted at the same or different positions.

[0106] Without violating common sense in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0107] The reagents and raw materials used in this invention are all commercially available.

[0108] The positive and progressive effects of this invention are as follows: compared with the currently commercially available flow battery cathode material 4-HO-TEMPO, the TEMPO molecules modified by the present invention through fluorine-containing groups have higher solubility, chemical stability and electrochemical stability, which significantly improves the energy density, rate performance and cycle life of flow batteries. Attached Figure Description

[0109] Figure 1 Example 1 and Control Group 1 were compared at 20 mA·cm -2 Comparison of long-cycle charge-discharge capacity under current density.

[0110] Figure 2 This is a comparison graph of the discharge capacity of Example 1 and Control Group 1 under different current densities.

[0111] Figure 3 This is a comparison graph of the energy efficiency and coulombic efficiency of Example 1 and Control Group 1 under different current densities. Detailed Implementation

[0112] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0113] Preparation Example 1: Synthesis of sodium 4-hydroxy-4-difluoroacetate-2,2,6,6-tetramethylpiperidine oxide:

[0114]

[0115] 2,2,6,6-Tetramethyl-4-piperidinone (77.6 g, 500 mmol) and Toluene (400 mL) were added sequentially to a 1 L reaction flask under argon anhydrous and oxygen-free protection. After cooling the solution to 0 °C, benzyl chloroformate (85.3 g, 500 mmol) was added dropwise. The mixture was pre-stirred for 5 minutes, and then reacted at 70 °C for 48 hours. After the reaction was completed, the solution was cooled to room temperature, diluted with 200 mL of ethyl acetate, and washed sequentially with 0.1 M dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine. The organic phase was separated, dried over anhydrous magnesium sulfate, and then filtered and concentrated. Purification by silica gel column chromatography (eluent: petroleum ether:ethyl acetate = 10:1) yielded 41.82 g of the expected product as a pale yellow solid, with a yield of 29%.

[0116]

[0117] To a 1L three-necked flask under argon-protected anhydrous and oxygen-free conditions, 19.52 g of 4-carbonyl-2,2,6,6-tetramethyl-1-carboxylic acid benzyl piperidine (6.62 g, 101.2 mmol), 6.62 g of activated Zn powder (200 mL), and tetrahydrofuran were added sequentially. The mixture was heated to 70 °C and refluxed. Ethyl bromodifluoroacetate (20.54 g, 101.2 mmol) was slowly added, and the mixture was refluxed at 70 °C for 6 hours. After the reaction was complete, the mixture was cooled to room temperature and washed sequentially with 1M dilute hydrochloric acid, saturated sodium bicarbonate solution, and saturated brine. The mixture was extracted three times with ethyl acetate, and the organic phase was separated, dried over anhydrous magnesium sulfate, and then filtered and concentrated. Purification by silica gel column chromatography (eluent: petroleum ether:ethyl acetate = 40:1) yielded 20.88 g of the expected product as a pale yellow solid, with a yield of 75%.

[0118]

[0119] 4-Difluoroethyl ethyl-4-hydroxy-2,2,6,6-tetramethyl-1-carboxylic acid benzyl ester-piperidine (20.88 g, 50.5 mmol), ethanol (100 mL), and 10% palladium / carbon (1.08 g, 1.02 mmol) were added sequentially to the jacket of an autoclave. Hydrogen was purged three times, and the autoclave was then purged with hydrogen at 30 atm. The reaction mixture was reacted at room temperature for 24 hours. The reaction solution was filtered and concentrated. Purification by silica gel column chromatography (eluent: petroleum ether:ethyl acetate = 20:1) yielded 12.13 g of the expected product as a white solid, in 86% yield.

[0120]

[0121] To a 500 mL reaction flask, ethyl 4-difluoroacetyl-4-hydroxy-2,2,6,6-tetramethylpiperidine (12.13 mg, 43.5 mmol) and diethyl ether (200 mL) were added sequentially. Then, m-chloroperoxybenzoic acid (17.64 g, 87.0 mmol) was added in four portions, 10 minutes apart, followed by reaction at room temperature for 2 hours. After the reaction was complete, the reaction solution was washed with saturated sodium bicarbonate solution and saturated brine. The organic phase was separated, dried over anhydrous magnesium sulfate, and concentrated by filtration. Purification by silica gel column chromatography (eluent: petroleum ether:ethyl acetate = 20:1) yielded 6.11 g of the expected product as an orange-yellow solid, in 48% yield.

[0122]

[0123] To a 500 mL reaction flask, 13.605 g (46.2 mmol) of ethyl 4-difluoroacetyl-4-hydroxy-2,2,6,6-tetramethylpiperidine oxide, 1.849 g (46.2 mmol) of NaOH, and a mixed solution of tetrahydrofuran / water (200 mL / 20 mL) were added sequentially, and the reaction was carried out at room temperature for 12 hours. The reaction solution was concentrated under reduced pressure, and the resulting solid was washed with 30 mL of water using DCM, followed by further concentration under reduced pressure to give 12.665 g of the expected product, an orange-yellow solid, with a yield of 95%.

[0124] Example 1

[0125] Step 1: Preparation of Electrolyte

[0126] The positive electrode active material and ammonium chloride were dissolved in deionized water to make the concentration of the positive electrode active material 0.2 mol·L⁻¹. -1 The concentration of ammonium chloride is 2.0 mol·L⁻¹. -1 The positive electrode electrolyte used in this embodiment was obtained. The molecular structure of sodium 4-difluoroacetate-4-hydroxy-2,2,6,6-tetramethylpiperidine oxide in Example 1 of the preparation of the positive electrode active material in this embodiment is shown below:

[0127]

[0128] The negative electrode active material and ammonium chloride were dissolved in deionized water to make the concentration of the negative electrode active material 0.4 mol·L⁻¹. -1 The concentration of ammonium chloride is 1.5 mol·L⁻¹. -1 The negative electrode electrolyte used in this embodiment was obtained. The negative electrode active material in this embodiment is zinc chloride.

[0129] Step 2: Fabrication of flow batteries

[0130] The components are stacked in the following order: clamp, insulating plate, copper current collector, zinc sheet, rubber gasket, flow guide plate (embedded with negative electrode graphite felt), sealing ring, diaphragm, sealing ring, flow guide plate (embedded with positive electrode graphite felt), rubber gasket, graphite bipolar plate, copper current collector, insulating plate, and clamp. The clamp is then secured with bolts. The copper current collector and zinc sheet are bonded together with conductive silver paste. The side with the zinc sheet is the negative electrode side of the flow battery, and the other side is the positive electrode side. The flow guide plate is 6mm thick with an active area of ​​25mm*25mm, and the zinc sheet is 25mm*25mm*4mm in size. The positive and negative electrode graphite felts are made of the same material; the positive electrode graphite felt is 25mm*25mm*7mm in size, and the negative electrode graphite felt is 25mm*25mm*4mm in size.

[0131] Take 20 mL of positive electrolyte and 20 mL of negative electrolyte and add them to the positive and negative electrode storage bottles respectively. Connect one end of the peristaltic pump hose to the inlet and outlet of the guide plate respectively, and insert the other end through the sealed bottle cap into the positive and negative electrode storage bottles. Turn on the peristaltic pump to circulate the electrolyte. After soaking for 2 to 24 hours, perform electrochemical tests.

[0132] Control group 1

[0133] The positive and negative electrode electrolytes and the flow battery were prepared using the same method as in Example 1, except that the positive electrode active material in the positive electrode electrolyte was 4-hydroxy-2,2,6,6-tetramethylpiperidine oxide, with the molecular structure shown below:

[0134]

[0135] The concentration of the positive electrode active material is 0.2 mol·L⁻¹. -1 The supporting electrolyte concentration is 2.0 mol·L⁻¹. -1 This serves as control group 1.

[0136] Effect Test Example: Battery Performance Test

[0137] 1. Charge-discharge long-cycle performance testing of fluorinated TEMPO derivatives as cathode materials

[0138] Batteries from Example 1 and Control Group 1 were subjected to long-cycle charge-discharge tests. The test voltage range was 1.0–2.0V, and the test current density was 20 mA·cm⁻¹. -2 100 charge-discharge cycles at a constant temperature of 30℃, see details. Figure 1 .

[0139] The discharge specific capacity data of the charge and discharge test are recorded in Table 1 below. The initial capacity is the discharge capacity of the first cycle, the remaining capacity is the discharge capacity of the last cycle, and the capacity retention rate represents the ratio of the remaining capacity to the initial capacity under the cycle conditions.

[0140] Table 1

[0141] sample Initial capacity (mAh) Remaining capacity (mAh) Capacity retention rate Control group 1 60.6 28.5 47.03％ Example 1 97.6 70.9 72.64％

[0142] 2. Charge / discharge rate performance testing of fluorinated TEMPO derivatives as cathode materials

[0143] The batteries obtained from Example 1 and Control Group 1 were subjected to rate performance testing, with a test voltage range of 1.0–2.0V. The test scheme involved sequentially applying voltages of 10, 20, 40, 60, 80, 100, 120, 140, and 160 mA·cm⁻¹. -2 Each current density was charged and discharged 5 times. See details... Figure 2 and 3 .

[0144] The rate performance test data are recorded in Tables 2 and 3 below. The average discharge capacity at each current density is the average of the discharge capacity over 5 cycles at that current density, and the average energy efficiency is the average of the energy efficiency over 5 cycles at that current density. Energy efficiency is the ratio of discharge energy to charge energy in a single cycle, and coulombic efficiency is the ratio of discharge capacity to charge capacity in a single cycle.

[0145] Table 2

[0146]

[0147] Table 3

[0148]

Claims

1. A positive electrode electrolyte, characterized in that, It includes compounds as shown in Formula I: ， Its definition is: R 1 is hydroxyl; X is C1-C4alkylene substituted by one or more F; 20 alkylene; R 2 -COOY a2 -SO2OY b2 or -PO(OY c2 )2; Y a2 , Y b2 and Y c2 are independently H or alkali metal; R 3 , R 4 , R 5 , and R 6 are independently C1-C6alkyl.

2. The positive electrode electrolyte as described in claim 1, characterized in that, The compound shown in Formula I satisfies one or more of the following conditions: (1) In X, the C1-C that is replaced by one or more F 20 C1-C in alkylene 20 The alkylene groups are C1-C6 alkylene groups; (2) In X, the C1-C that is replaced by one or more F 20 The plurality of alkylene groups is 2, 3 or 4; (3) Y a2 Y b2 and Y c2 In this context, the alkali metal is Li, Na, K, Rb, or Cs; (4) R 3 R 4 R 5 and R 6 In this context, the C1-C6 alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, or tert-butyl.

3. The positive electrode electrolyte as described in claim 2, characterized in that, The compound shown in Formula I satisfies one or more of the following conditions: (1) In X, the C1-C that is replaced by one or more F 20 C1-C in alkylene 20 The alkylene group is methylene. , , , , , or ; (2) In X, the C1-C that is replaced by one or more F 20 The alkylene groups consist of two or more; (3) Y a2 Y b2 and Y c2 In this context, the alkali metal is Na.

4. The positive electrode electrolyte as described in claim 3, characterized in that, In X, the C1-C that is replaced by one or more F 20 C1-C in alkylene 20 The alkylene group is methylene.

5. The positive electrode electrolyte as described in claim 1, characterized in that, R 1 It is a hydroxyl group; X is a C1-C molecule replaced by one or more F molecules. 20 Alkylene; R 2 -COOY a2 -SO2OY b2 or -PO(OY c2 )2; Y a2 Y b2 and Y c2 It is an alkali metal on its own.

6. The positive electrode electrolyte as described in claim 5, characterized in that, R 1 It is a hydroxyl group; X is a C1-C molecule replaced by one or more F molecules. 20 Alkylene; R 2 -COOY a2 ; Y a2 It is an alkali metal.

7. The positive electrode electrolyte as described in claim 1, characterized in that, The compound represented by Formula I is any one of the following compounds: , or .

8. The positive electrode electrolyte as described in any one of claims 1-7, characterized in that, The positive electrode electrolyte also includes a supporting electrolyte and a solvent; the supporting electrolyte is one or more of KCl, KOH, KOCH3, NaCl, NaOH, NaOAc, NaNO3, Na2SO4, LiPF6, LiBF4, LiCF3SO3, LiB(CO2CO2)2, LiBF2(CO2CO2), LiCl, LiN(SO2CF2CF3)2, LiN(SO2CF3)2, LiN(SO2F)2, ZnCl2, or NH4Cl.

9. The positive electrode electrolyte as described in claim 8, characterized in that, The positive electrode electrolyte satisfies one or more of the following conditions (1)-(4): (1) The concentration of the compound represented by Formula I is 0.1 mol / L-3 mol / L; (2) The supporting electrolyte is NH4Cl; (3) The concentration of the supporting electrolyte is 0.5 mol / L-4 mol / L; (4) The solvent is water and / or an organic solvent.

10. The positive electrode electrolyte as described in claim 9, characterized in that, The positive electrode electrolyte meets one or two of the following conditions: (1) The concentration of the compound represented by Formula I is 0.2 mol / L-2 mol / L; (2) The concentration of the supporting electrolyte is 2 mol / L.

11. The positive electrode electrolyte as described in claim 10, characterized in that, The concentration of the compound represented by Formula I is 0.2 mol / L.

12. The positive electrode electrolyte as described in claim 9, characterized in that, The positive electrode electrolyte consists of 0.2 mol / L... It consists of 2.0 mol / L ammonium chloride and water.

13. The positive electrode electrolyte as described in any one of claims 1-7, characterized in that, The compound shown in Formula I is prepared from the compound shown in Formula II: ； Among them, X and R 1 R 3 R 4 R 5 and R 6 The definition is as described in any one of claims 1-7, R 12 -COOR 13a -SO2OR 13b or -PO(OR) 13c )2; R 13a R 13b and R 13c It is an alkyl group that is independently C1-C6.

14. The positive electrode electrolyte as described in claim 13, characterized in that, The compound represented by Formula II is any one of the following compounds: 。 15. A method for preparing a positive electrode electrolyte as described in any one of claims 1-7, characterized in that, It includes the following steps: under the action of an alkaline reagent, compound II is hydrolyzed in a solvent to obtain compound I as shown below; ； R 12 -COOR 13a -SO2OR 13b or -PO(OR) 13c )2; R 13a R 13b and R 13c Alkyl groups that are independently C1-C6; X, R 1 R 2 R 3 R 4 R 5 and R 6 The definitions are as described in any one of claims 1-7.

16. The preparation method according to claim 15, characterized in that, The preparation method described herein satisfies one or more of the following conditions: (1) The alkaline reagent is an alkali metal base; (2) The solvent is a mixture of ether solvent and water; (3) The hydrolysis reaction is carried out at room temperature.

17. The preparation method according to claim 16, characterized in that, The preparation method described herein satisfies one or more of the following conditions: (1) The alkali metal base mentioned is LiOH, NaOH, KOH or CsOH; (2) The volume ratio of the ether solvent to water is 5:1-30:1; (3) The ether solvent is tetrahydrofuran.

18. The application of a positive electrode electrolyte as described in any one of claims 1-14 in a flow battery; the flow battery comprising the positive electrode electrolyte, ZnCl2, NH4Cl, water, electrodes, bipolar plates, flow guide plates, and a separator.

19. The application as described in claim 18, characterized in that, The electrode is a porous electrode or a metal mesh; The bipolar plate is a graphite bipolar plate; The guide plate has a cavity for placing the electrode, and an inlet and an outlet connected to the cavity; The membrane is an ion exchange membrane or a porous membrane.

20. The application as described in claim 19, characterized in that, The electrode is a graphite felt; when the electrode is placed in the cavity of the flow guide plate, one side of the electrode is in contact with the bipolar plate, and the other side of the electrode is in contact with the diaphragm; the diaphragm is a cation exchange membrane.

21. The application as described in claim 20, characterized in that, The electrodes are positive graphite felt and negative graphite felt.

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