A membrane-free dual-phase vanadium-bromine battery and its electrolyte

Abstract

The present invention relates to the technical field of membrane-free batteries, and particularly to a membrane-free biphasic vanadium-bromine battery and its electrolyte. In the membrane-free biphasic vanadium-bromine battery of the present invention, water and organic solvents are used to avoid self-discharge of the battery caused by cross-contamination of active substances on the premise of avoiding a diaphragm. Bromide ions in potassium bromide serve as cross-phase redox substances, and vanadium ions in vanadyl sulfate serve as non-cross-phase redox substances. A bromine complexing agent is added to the organic solvent to combine with bromine to form a highly soluble hydrophobic active substance, reducing the battery cost, simplifying the device design, enhancing the battery's theoretical capacity, and avoiding a series of battery cycle and lifespan problems caused by irregular growth of zinc metal.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane-free batteries, and particularly to a membrane-free biphasic vanadium-bromine battery and its electrolyte solution. Background Art

[0002] Ion exchange membranes are widely used in redox flow batteries, which can effectively prevent the cross-diffusion of active substances and reduce self-discharge. However, the irreversible reactions, low coulombic efficiency, and capacity decay caused by the transport of redox substances through the membrane are still one of the main reasons for the performance degradation of flow batteries. Although certain progress has been made in the research and development of high-performance ion exchange membranes in recent years, the improvement amplitude is limited. In addition, the existing ion exchange membranes are costly, accounting for approximately 20% of the total battery cost, and their service life cannot meet the requirements of long-term energy storage systems. To address these challenges, membrane-free battery technology not only reduces the cost of energy storage systems but also reduces the performance degradation problems caused by the aging of membrane materials, thereby improving the reliability and service life of the system. These characteristics make membrane-free batteries one of the promising candidate technologies for large-scale energy storage.

[0003] The existing biphasic membrane-free systems mainly use anthraquinone, tetramethylpiperidine oxide organic compounds, or metallic zinc as active substances in the electrolyte solution. In the organic compound system, the solubility of the active substances is usually low, which directly limits the concentration of substances in the electrolyte solution, resulting in a relatively limited theoretical capacity of the battery and an inability to fully improve the energy density. In the zinc system, although zinc has a high theoretical capacity, during the charge-discharge cycle, zinc metal will deposit in a solid form, affecting the long-term stability of the battery. The formation of zinc deposition may also lead to dendrite growth, causing changes in the internal structure of the battery, limiting the actual achievable capacity of the battery, and thus reducing the overall performance of the system. The deposition and shedding of zinc dendrites will also reduce the coulombic efficiency of the battery, resulting in capacity decay and shortening the service life of the battery. In addition, the uneven growth of zinc dendrites may also cause an increase in the internal resistance of the battery, affecting the overall performance stability of the battery. Summary of the Invention

[0004] Aiming at the deficiencies of the above-mentioned existing technologies, the purpose of the present invention is to provide a membrane-free biphasic vanadium-bromine battery and its electrolyte solution. In the membrane-free biphasic vanadium-bromine battery of the present invention, water and organic solvents are used to avoid self-discharge of the battery caused by cross-contamination of active substances without using a diaphragm. Bromide ions in potassium bromide are used as cross-phase redox substances, and vanadium ions in vanadyl sulfate are used as non-cross-phase redox substances. A bromine complexing agent is added to the organic solvent to combine with bromine to form a highly soluble hydrophobic active substance. Moreover, no solid products are generated during the charge-discharge process of the electrolyte solution of the present invention, reducing the battery cost, simplifying the device design, increasing the theoretical capacity of the battery, and avoiding a series of battery cycle and life problems caused by the irregular growth of zinc metal.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A membrane-free biphasic vanadium-bromine battery electrolyte, wherein the electrolyte comprises an aqueous anolyte and a non-aqueous catholyte with a volume ratio of 1:0.5 to 1.

[0007] The aqueous anolyte comprises water, an anodic active material, and an anolyte additive. The anodic active material is vanadyl sulfate with a concentration of 0.05 mol / L to 2.5 mol / L, and the anolyte additive is an alkali metal bromide salt with a concentration of 0.05 mol / L to 2 mol / L.

[0008] The non-aqueous catholyte comprises a non-aqueous solvent and a catholyte additive. The catholyte additive is sulfated α-cyclodextrin, hydroxypropyl-β-cyclodextrin, or tetra-decyl ammonium bromide.

[0009] When the catholyte additive is sulfated α-cyclodextrin, the concentration of the catholyte additive is 0.02 mol / L to 1 mol / L; when the catholyte additive is hydroxypropyl-β-cyclodextrin, the concentration of the catholyte additive is 0.05 mol / L to 1 mol / L; when the catholyte additive is tetra-decyl ammonium bromide, the concentration of the catholyte additive is 0.05 mol / L to 3 mol / L.

[0010] The membrane-free biphasic vanadium-bromine battery electrolyte of the present invention comprises an aqueous anolyte and a non-aqueous catholyte. Among them, the aqueous anolyte comprises water, an anodic active material, and an anolyte additive, and the non-aqueous catholyte comprises a non-aqueous solvent and a catholyte additive. Using vanadyl sulfate as the anodic active material, an alkali metal bromide salt as the anolyte additive, bromide ions in potassium bromide as the cross-phase redox substance, and vanadium ions in vanadyl sulfate as the non-cross-phase redox substance, a bromine complexing agent sulfated α-cyclodextrin, hydroxypropyl-β-cyclodextrin, or tetra-decyl ammonium bromide is added to the non-aqueous solvent to form a highly soluble hydrophobic active substance by combining with bromine. By improving the solubility of the active substance, the capacity density of the battery system is further improved, ensuring the efficient energy storage and release of the overall battery. Using trivalent vanadium and tetravalent vanadium ions as the negative electrode redox pair effectively avoids the problems of poor electrochemical stability and performance degradation of the battery caused by the formation of metal solid products during the cycling process, improves the theoretical capacity of the battery, and avoids a series of battery cycling and life problems caused by irregular growth of zinc metal. Moreover, the membrane-free biphasic vanadium-bromine battery electrolyte prepared by the present invention generates no solid products during the charge and discharge process. Different from other bromine-based electrolytes, it is paired with vanadium rather than a zinc anolyte to avoid the battery side reactions and failure problems caused by the generation of zinc metal solids during the charging process.

[0011] In a preferred embodiment of the present invention, when the additive of the catholyte is sulfated α-cyclodextrin, the concentration of the additive of the catholyte is 0.05 mol / L to 0.75 mol / L; when the additive of the catholyte is hydroxypropyl-β-cyclodextrin, the concentration of the additive of the catholyte is 0.07 mol / L to 0.75 mol / L; when the additive of the catholyte is tetra-decyl ammonium bromide, the concentration of the additive of the catholyte is 0.07 mol / L to 1.8 mol / L.

[0012] In a preferred embodiment of the present invention, the concentration of the anode active material is 0.75 mol / L to 1.5 mol / L.

[0013] In a preferred embodiment of the present invention, the alkali metal bromide is potassium bromide or sodium bromide.

[0014] In a preferred embodiment of the present invention, the concentration of the additive of the anolyte is 0.3 mol / L to 1.75 mol / L.

[0015] In a preferred embodiment of the present invention, the non-aqueous solvent is an organic solvent.

[0016] In a preferred embodiment of the present invention, the organic solvent is carbon tetrachloride or tetrachloroethylene.

[0017] Another object of the present invention is to provide a membrane-free biphasic vanadium bromine battery, comprising a battery body and the membrane-free biphasic vanadium bromine battery electrolyte according to any one of the above.

[0018] In a preferred embodiment of the present invention, the battery body includes a cathode, an anode and battery devices, the battery container is provided with the cathode and the anode, and the battery container is filled with the membrane-free biphasic vanadium bromine battery electrolyte.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. The electrolyte of the membrane-free biphasic vanadium-bromine battery of the present invention includes an aqueous anolyte and a non-aqueous catholyte. Among them, the aqueous anolyte includes water, an anodic active material, and an anolyte additive, and the non-aqueous catholyte includes a non-aqueous solvent and a catholyte additive. Vanadyl sulfate is used as the anodic active material, and an alkali metal bromide is used as the anolyte additive. The bromide ion in the alkali metal bromide is used as a cross-phase redox substance, and the vanadium ion in vanadyl sulfate is used as a non-cross-phase redox substance. A bromine complexing agent, sulfated α-cyclodextrin, hydroxypropyl-β-cyclodextrin, or tetra-decyl ammonium bromide, is added to the non-aqueous solvent to form a highly soluble hydrophobic active substance by combining with bromine. By improving the solubility of the active substance, the capacity density of the battery system is further improved, ensuring the efficient energy storage and release of the overall battery. In addition, using trivalent vanadium and tetravalent vanadium ions as the negative electrode redox pair effectively avoids the problems of poor electrochemical stability and performance degradation of the battery caused by the formation of metal solid products during the cycling process, improves the theoretical capacity of the battery, and avoids a series of battery cycling and lifespan problems caused by the irregular growth of zinc metal. Moreover, the electrolyte of the membrane-free biphasic vanadium-bromine battery prepared by the present invention does not generate any solid products during the charge and discharge process. Different from other bromine-based electrolytes, using vanadium instead of zinc anolyte avoids the side reactions and failure problems of the battery caused by the generation of zinc metal solids during the charging process.

[0021] 2. In the membrane-free biphasic vanadium-bromine battery of the present invention, water and organic solvents are used to avoid self-discharge of the battery caused by cross-contamination of active substances without using a separator. The design of the present invention, without using a high-cost separator, has a special design that does not generate metal solids during the charging process, maintaining the long-term operation stability of the battery while significantly improving its performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the reaction schematic diagram of the membrane-free biphasic vanadium-bromine battery of the present invention.

[0023] Figure 2 Among them, (a) is the reaction result diagram before charging, and (b) is the reaction result diagram after charging.

[0024] Figure 3 is the Coulomb efficiency of the membrane-free biphasic vanadium-bromine battery prepared in Example 1 of the present invention after 50 cycles.

[0025] Figure 4 is the open-circuit voltage diagram of the membrane-free biphasic vanadium-bromine battery prepared in Example 2 of the present invention within 80 hours.

[0026] Figure 5 is the voltage-time diagram of the membrane-free biphasic vanadium-bromine battery prepared in Example 3 of the present invention after 150 hours of cycling.

[0027] Figure 6The figure shows the results of the continuous charging voltage of the membraneless dual-phase vanadium-bromine battery prepared in Example 4 of the present invention for 25 hours.

[0028] Figure 7 The figure shows the electrode condition of the membraneless dual-phase vanadium-bromine battery prepared in Example 4 of the present invention after 25 hours of continuous charging.

[0029] Figure 8 The figure shows the battery condition of the battery prepared in Comparative Example 1 of the present invention after continuous charging. Detailed implementation manners

[0030] The following combines the embodiments of the present invention, and uses preferred embodiments and accompanying drawings for detailed description. The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] It should be noted that all the professional terms used in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the following embodiments of the present invention can be obtained through the market or prepared by existing methods.

[0032] Example 1

[0033] An electrolyte for a membraneless dual-phase vanadium-bromine battery, 0.9 mol / L tetrabutylammonium bromide in tetrachloroethylene as the organic phase, and 1 mol / L potassium bromide and 1 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volumes of the cathode and anode electrolytes are both 6 mL, and the organic phase and the aqueous phase are mixed to obtain a dual-phase electrolyte.

[0034] A membraneless dual-phase vanadium-bromine battery, the positive and negative electrodes are titanium plate electrodes respectively, and the current collectors on both sides are titanium wires with a length of 8 cm and a diameter of 4 mm. The above-mentioned dual-phase electrolyte is used as the electrolyte of the membraneless dual-phase vanadium-bromine battery, and the electrolyte is naturally stratified to assemble a membraneless dual-phase vanadium-bromine battery.

[0035] The membraneless dual-phase vanadium-bromine battery in Example 1 was cycled at a current density of 2.5 mA / cm 2 and a capacity of 10 mAh, with a cut-off voltage of 0 - 1.9 V. The results are as Figure 3 shown. After 50 cycles, no capacity decay was observed, the average Coulombic efficiency was 88.28%, and no solid products were observed during the charge and discharge process.

[0036] Figure 1 This is the reaction principle diagram of the membraneless dual-phase vanadium-bromine battery of the present invention. The anodic reaction is E0 = 0.337 V; The cathode reaction is: E 0 = 1.087 V. Figure 2 Among them, (a) is the reaction result diagram before charging, and (b) is the reaction result diagram after charging. It can be seen that during the charging process, the upper layer solution changes from blue to dark green, and the lower layer solution changes from transparent to red, proving the formation of charging products, and no solid products are formed during the charging and discharging processes.

[0037] Example 2

[0038] An electrolyte for a membrane-free dual-phase vanadium-bromine battery, 0.1 mol / L sulfated α-cyclodextrin in tetrachloroethylene as the organic phase, 0.3 mol / L sodium bromide and 0.5 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volume of the anode electrolyte is 7 mL, and the volume of the cathode electrolyte is 4.5 mL. The organic phase and the aqueous phase are mixed to obtain a dual-phase electrolyte.

[0039] A membrane-free dual-phase vanadium-bromine battery, the positive and negative electrodes are titanium plate electrodes respectively, and the current collectors on both sides are titanium wires with a length of 6 cm and a diameter of 3.5 mm. The above dual-phase electrolyte is used as the electrolyte for the membrane-free dual-phase vanadium-bromine battery, and the electrolyte is naturally layered to assemble a membrane-free dual-phase vanadium-bromine battery.

[0040] The membrane-free dual-phase vanadium-bromine battery in Example 2 is charged to 10 mAh at a current density of 1 mA / cm 2 The result is as Figure 4 shown. The open-circuit voltage of the battery remains stable within 80 hours, only dropping by 0.0971 V.

[0041] Example 3

[0042] An electrolyte for a membrane-free dual-phase vanadium-bromine battery, 0.7 mol / L hydroxypropyl-β-cyclodextrin in carbon tetrachloride as the organic phase, 1.3 mol / L sodium bromide and 1 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volume of the anode electrolyte is 6 mL, and the volume of the cathode electrolyte is 3.5 mL. The organic phase and the aqueous phase are mixed to obtain a dual-phase electrolyte.

[0043] A membrane-free dual-phase vanadium-bromine battery, the positive and negative electrodes are a titanium plate electrode and an aluminum foil electrode respectively, and the current collectors on both sides are aluminum wires with a length of 6 cm and a diameter of 3.5 mm. The above dual-phase electrolyte is used as the electrolyte for the membrane-free dual-phase vanadium-bromine battery, and the electrolyte is naturally layered to assemble a membrane-free dual-phase vanadium-bromine battery.

[0044] The membrane-free dual-phase vanadium-bromine battery in Example 3 is cycled at a current density of 1 mA / cm 2 with a capacity of 5 mAh, and the cut-off voltage is 0 - 1.3 V. The result is as Figure 5As shown, no capacity attenuation was observed after 150 hours of cycling, the voltage was stable, and no solid products were generated during the charge and discharge process.

[0045] Example 4

[0046] An electrolyte for a membrane-free biphasic vanadium-bromine battery, 1.5 mol / L tetrabutylammonium bromide in carbon tetrachloride as the organic phase, 1 mol / L sodium bromide and 0.8 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volume of the anolyte is 6 mL, and the volume of the catholyte is 3.5 mL. The organic phase and the aqueous phase are mixed to obtain a biphasic electrolyte.

[0047] A membrane-free biphasic vanadium-bromine battery, with the positive and negative electrodes being titanium plate electrodes and aluminum foil electrodes respectively. The current collectors on both sides are aluminum wires with a length of 6 cm and a diameter of 3.5 mm. The above biphasic electrolyte is used as the electrolyte for the membrane-free biphasic vanadium-bromine battery. The biphasic electrolyte is assisted by two peristaltic pumps to flow and circulate at a rate of 30 mL / min, and a membrane-free biphasic vanadium-bromine battery is assembled.

[0048] The membrane-free biphasic vanadium-bromine battery in Example 4 was charged at a constant current density of 1.0 mA / cm 2 until the cut-off voltage was 1.0 V. The results are as Figure 6 shown. The charging voltage was stable during 25 hours of continuous charging, and it can be seen from the electrode condition diagram of the battery after 25 hours of charge and discharge in Figure 7 that no solid products were generated on the electrodes during the charging and discharging processes.

[0049] Example 5

[0050] An electrolyte for a membrane-free biphasic vanadium-bromine battery, 0.07 mol / L tetrabutylammonium bromide in tetrachloroethylene as the organic phase, 0.05 mol / L potassium bromide and 0.05 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volume of both the catholyte and the anolyte is 6 mL. The organic phase and the aqueous phase are mixed to obtain a biphasic electrolyte.

[0051] A membrane-free biphasic vanadium-bromine battery, with the positive and negative electrodes being titanium plate electrodes. The current collectors on both sides are titanium wires with a length of 8 cm and a diameter of 4 mm. The above biphasic electrolyte is used as the electrolyte for the membrane-free biphasic vanadium-bromine battery, and the electrolyte naturally stratifies to assemble a membrane-free biphasic vanadium-bromine battery.

[0052] Example 6

[0053] An electrolyte for a membrane-free biphasic vanadium-bromine battery, 1.8 mol / L tetrabutylammonium bromide in tetrachloroethylene as the organic phase, 2 mol / L potassium bromide and 2.5 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volume of both the catholyte and the anolyte is 6 mL. The organic phase and the aqueous phase are mixed to obtain a biphasic electrolyte.

[0054] A membrane-free biphasic vanadium-bromine battery, with the positive and negative electrodes being titanium plate electrodes respectively, and the current collectors on both sides being titanium wires with a length of 8 cm and a diameter of 4 mm. The above-mentioned biphasic electrolyte is used as the electrolyte of the membrane-free biphasic vanadium-bromine battery, and the electrolyte is assembled into a membrane-free biphasic vanadium-bromine battery by natural stratification.

[0055] Example 7

[0056] An electrolyte for a membrane-free biphasic vanadium-bromine battery, 3 mol / L tetrabutylammonium bromide in tetrachloroethylene as the organic phase, 1.75 mol / L potassium bromide and 1.5 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volumes of the cathode and anode electrolytes are both 6 mL, and the organic phase and the aqueous phase are mixed to obtain a biphasic electrolyte.

[0057] A membrane-free biphasic vanadium-bromine battery, with the positive and negative electrodes being titanium plate electrodes respectively, and the current collectors on both sides being titanium wires with a length of 8 cm and a diameter of 4 mm. The above-mentioned biphasic electrolyte is used as the electrolyte of the membrane-free biphasic vanadium-bromine battery, and the electrolyte is assembled into a membrane-free biphasic vanadium-bromine battery by natural stratification.

[0058] Example 8

[0059] An electrolyte for a membrane-free biphasic vanadium-bromine battery, 0.05 mol / L sulfated α-cyclodextrin in tetrachloroethylene as the organic phase, 0.3 mol / L sodium bromide and 0.5 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volume of the anode electrolyte is 7 mL, and the volume of the cathode electrolyte is 4.5 mL. The organic phase and the aqueous phase are mixed to obtain a biphasic electrolyte.

[0060] A membrane-free biphasic vanadium-bromine battery, with the positive and negative electrodes being titanium plate electrodes respectively, and the current collectors on both sides being titanium wires with a length of 6 cm and a diameter of 3.5 mm. The above-mentioned biphasic electrolyte is used as the electrolyte of the membrane-free biphasic vanadium-bromine battery, and the electrolyte is assembled into a membrane-free biphasic vanadium-bromine battery by natural stratification.

[0061] Example 9

[0062] An electrolyte for a membrane-free biphasic vanadium-bromine battery, 0.75 mol / L sulfated α-cyclodextrin in tetrachloroethylene as the organic phase, 0.3 mol / L sodium bromide and 0.5 mol / L vanadyl sulfate in deionized water as the aqueous phase. The volume of the anode electrolyte is 7 mL, and the volume of the cathode electrolyte is 4.5 mL. The organic phase and the aqueous phase are mixed to obtain a biphasic electrolyte.

[0063] A membrane-free biphasic vanadium-bromine battery, with the positive and negative electrodes being titanium plate electrodes respectively, and the current collectors on both sides being titanium wires with a length of 6 cm and a diameter of 3.5 mm. The above-mentioned biphasic electrolyte is used as the electrolyte of the membrane-free biphasic vanadium-bromine battery, and the electrolyte is assembled into a membrane-free biphasic vanadium-bromine battery by natural stratification.

[0064] Example 10

[0065] A membrane-free biphasic vanadium-bromine battery electrolyte, where 0.07 mol / L of hydroxypropyl-β-cyclodextrin in carbon tetrachloride serves as the organic phase, and 1.3 mol / L of sodium bromide and 1 mol / L of vanadyl sulfate in deionized water serve as the aqueous phase. The volume of the anolyte is 6 mL, and the volume of the catholyte is 3.5 mL. The organic phase and the aqueous phase are mixed to obtain the biphasic electrolyte.

[0066] A membrane-free biphasic vanadium-bromine battery, with the positive and negative electrodes being titanium plate electrodes and aluminum foil electrodes respectively. The current collectors on both sides are aluminum wires with a length of 6 cm and a diameter of 3.5 mm. The above biphasic electrolyte serves as the electrolyte of the membrane-free biphasic vanadium-bromine battery, and the electrolyte naturally layers to assemble the membrane-free biphasic vanadium-bromine battery.

[0067] Example 11

[0068] A membrane-free biphasic vanadium-bromine battery electrolyte, where 1 mol / L of hydroxypropyl-β-cyclodextrin in carbon tetrachloride serves as the organic phase, and 1.3 mol / L of sodium bromide and 1 mol / L of vanadyl sulfate in deionized water serve as the aqueous phase. The volume of the anolyte is 6 mL, and the volume of the catholyte is 3.5 mL. The organic phase and the aqueous phase are mixed to obtain the biphasic electrolyte.

[0069] A membrane-free biphasic vanadium-bromine battery, with the positive and negative electrodes being titanium plate electrodes and aluminum foil electrodes respectively. The current collectors on both sides are aluminum wires with a length of 6 cm and a diameter of 3.5 mm. The above biphasic electrolyte serves as the electrolyte of the membrane-free biphasic vanadium-bromine battery, and the electrolyte naturally layers to assemble the membrane-free biphasic vanadium-bromine battery.

[0070] During the charging and discharging processes of the membrane-free biphasic vanadium-bromine batteries prepared in Examples 5 to 11, no solid products are formed on the electrodes.

[0071] Comparative Example 1

[0072] When using a traditional zinc electrolyte as the anolyte, 1.5 mol / L of tetrabutylammonium bromide in tetrachloroethylene serves as the organic phase, and 1 mol / L of potassium bromide and 0.8 mol / L of zinc bromide in deionized water serve as the aqueous phase. The battery is assembled by mixing the two electrolytes together and then allowing them to naturally layer. The anolyte is 6 mL, and the catholyte is 3.5 mL. The battery is charged at a constant current density of 1.0 mA / cm 2 until the cut-off voltage is 1.0 V. The results are as Figure 8 shown, and a large amount of zinc metal is generated and accumulates in the two-phase electrolyte during charging, resulting in battery failure.

[0073] In summary, the electrolyte of the membraneless biphasic vanadium-bromine battery of the present invention includes an aqueous anolyte and a non-aqueous catholyte. Among them, the aqueous anolyte includes water, an anodic active material, and an anolyte additive, and the non-aqueous catholyte includes a non-aqueous solvent and a catholyte additive. Vanadyl sulfate is used as the anodic active material, an alkali metal bromide is used as the anolyte additive, bromide ions in potassium bromide are used as the cross-phase redox substance, and vanadium ions in vanadyl sulfate are used as the non-cross-phase redox substance. A bromine complexing agent, sulfated α-cyclodextrin, hydroxypropyl-β-cyclodextrin, or tetrabutylammonium bromide, is added to the non-aqueous solvent to combine with bromine to form a highly soluble hydrophobic active substance. By improving the solubility of the active substance, the capacity density of the battery system is further improved, ensuring the efficient energy storage and release of the overall battery. Using trivalent vanadium and tetravalent vanadium ions as the negative electrode redox pair effectively avoids the problems of poor electrochemical stability and performance degradation of the battery caused by the formation of metal solid products during the cycling process, improves the theoretical capacity of the battery, and avoids a series of battery cycling and lifespan problems caused by irregular growth of zinc metal. Moreover, the membraneless biphasic vanadium-bromine battery electrolyte prepared by the present invention does not generate any solid products during the charge and discharge process. Different from other bromine-based electrolytes, it is paired with a vanadium rather than a zinc anolyte to avoid the problems of battery side reactions and failure caused by the generation of zinc metal solids during the charging process.

[0074] It should be noted that when the present invention involves a numerical range, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the adopted step methods are the same as those of the embodiments, to prevent repetition, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the scope of the appended protection is intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0075] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the present invention and its equivalent technologies, the present invention also intends to include these modifications and variations.

Claims

1. A membrane-free biphasic vanadium bromine battery electrolyte, characterized in that, The electrolyte includes an anolyte in an aqueous phase with a volume ratio of 1:0.5 - 1 and a catholyte in a non-aqueous phase; The anolyte in the aqueous phase includes water, an anodic active material, and an anolyte additive. The anodic active material is vanadyl sulfate, the concentration of the anodic active material is 0.05 mol / L - 2.5 mol / L, the anolyte additive is an alkali metal bromide, and the concentration of the anolyte additive is 0.05 mol / L - 2 mol / L; The catholyte in the non-aqueous phase includes a non-aqueous solvent and a catholyte additive. The catholyte additive is sulfated α-cyclodextrin, hydroxypropyl-β-cyclodextrin, or tetrabutylammonium bromide; When the catholyte additive is sulfated α-cyclodextrin, the concentration of the catholyte additive is 0.02 mol / L - 1 mol / L. When the catholyte additive is hydroxypropyl-β-cyclodextrin, the concentration of the catholyte additive is 0.05 mol / L - 1 mol / L. When the catholyte additive is tetrabutylammonium bromide, the concentration of the catholyte additive is 0.05 mol / L - 3 mol / L; The electrolyte of the membrane-free biphasic vanadium-bromine battery naturally stratifies and is applicable to a membrane-free biphasic vanadium-bromine battery.

2. The electrolyte of the membrane-free dual-phase vanadium-bromine battery according to claim 1, wherein When the catholyte additive is sulfated α-cyclodextrin, the concentration of the catholyte additive is 0.05 mol / L - 0.75 mol / L. When the catholyte additive is hydroxypropyl-β-cyclodextrin, the concentration of the catholyte additive is 0.07 mol / L - 0.75 mol / L. When the catholyte additive is tetrabutylammonium bromide, the concentration of the catholyte additive is 0.07 mol / L - 1.8 mol / L.

3. The membrane-free biphasic vanadium-bromine battery electrolyte according to claim 1, wherein The concentration of the anodic active material is 0.75 mol / L - 1.5 mol / L.

4. The electrolyte of the membrane-free biphasic vanadium-bromine battery according to claim 1, wherein The alkali metal bromide is potassium bromide or sodium bromide.

5. The electrolyte of the membrane-free dual-phase vanadium-bromine battery according to claim 1, characterized in that, The concentration of the anolyte additive is 0.3 mol / L - 1.75 mol / L.

6. The electrolyte of the membrane-free dual-phase vanadium-bromine battery according to claim 1, characterized in that, The non-aqueous solvent is an organic solvent.

7. The membrane-free biphasic vanadium bromine battery electrolyte according to claim 6, characterized in that, The organic solvent is carbon tetrachloride or tetrachloroethylene.

8. A membrane-free biphasic vanadium bromine battery, characterized in that, It includes a battery body and the electrolyte of the membrane-free biphasic vanadium-bromine battery according to any one of claims 1 - 7.

9. The membraneless biphasic vanadium-bromine battery according to claim 8, wherein, The battery body includes a cathode, an anode, and battery devices. The battery container is provided with the cathode and the anode, and the battery container is filled with the electrolyte of the membrane-free biphasic vanadium-bromine battery.

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