A vanadium electrolytic liquid crystal and a cyclic preparation method thereof

Abstract

The invention provides a vanadium electrolytic liquid crystal and a cyclic preparation method thereof. The cyclic preparation method of the vanadium electrolytic liquid crystal comprises the following steps: dissolving VO2 with H2SO4 to obtain a VOSO4 solution; using the VOSO4 solution as a positive electrode and a negative electrode to perform electrolysis; heating the positive electrode solution to precipitate vanadium, filtering to obtain red vanadium and filtrate A; adding sulfuric acid to the negative electrode solution, cooling and crystallizing, filtering to obtain V2(SO4)3*nH2O crystals and filtrate B; mixing red vanadium, V2(SO4)3*nH2O crystals and concentrated sulfuric acid, solidifying and forming, and obtaining a vanadium electrolytic liquid crystal; mixing the filtrate A and the filtrate B, adding V2O5 and V2O3 to adjust the valence of vanadium in the solution, adding VO2 and H2SO4 to adjust the total vanadium and sulfate concentrations, obtaining a VOSO4 solution, and the VOSO4 solution is returned to step 2 for circulation. The method of the invention has simple steps, low cost, and no pollution, and can realize the industrialized continuous production of vanadium electrolytic liquid crystals.

Description

Technical Field

[0001] The invention relates to vanadium electrolyte technology, in particular to a vanadium electrolytic liquid crystal and a cyclic preparation method thereof. Background Art

[0002] In my country's national economic planning, it is clearly pointed out that we should strengthen the connection between sources, grids, loads and storage, improve the consumption and storage capacity of clean energy, and accelerate the construction of energy storage power stations and the large-scale application of new energy storage technologies. All-vanadium liquid flow batteries are the preferred technology in the field of large-capacity energy storage. Compared with traditional lithium batteries and lead-acid batteries in the large-scale energy storage industry, they have distinct technical advantages such as good safety performance, green environmental protection, long cycle life, high energy conversion rate, fast response speed, deep discharge, and suitability for large current charging and discharging. They can make up for the fact that lithium batteries and lead-acid batteries are difficult to meet the development needs of large-capacity energy storage, and their application value is increasingly valued.

[0003] As a key material for all-vanadium flow batteries, the cost and quality of vanadium electrolytes affect the development of the vanadium battery industry. As a research and development hotspot, new vanadium electrolyte liquid crystals have received much attention. While ensuring product quality, vanadium electrolyte liquid crystals reduce packaging and transportation costs, and enhance the market competitiveness of all-vanadium flow batteries.

[0004] At present, vanadium electrolytic liquid crystals are prepared by preparing (VO2)2SO4, VOSO4, V2(SO4)3, and VSO4 respectively, adjusting the valence states, and adding concentrated sulfuric acid. Among them, (VO2)2SO4 and VOSO4 can be prepared in a cycle by dissolving vanadium oxide in sulfuric acid. V2(SO4)3 and VSO4 are mainly obtained by electrolysis. The positive electrode solution after electrolysis needs to be prepared in a cycle by adding a restoring agent and the negative electrode solution needs to be added with an oxidant. The use of restoring agents and oxidants not only increases the preparation cost of vanadium electrolytic liquid crystals, but also has the risk of introducing impurities and contaminating products. Summary of the invention

[0005] The purpose of the present invention is to propose a method for cyclically preparing vanadium electrolytic liquid crystals, aiming at the problems that the traditional vanadium electrolytic liquid crystal preparation process has electric energy waste, auxiliary materials in the recovery process increase the preparation cost of vanadium electrolyte, and introduce impurities. The method has simple steps, low cost, and no pollution, and can realize the industrialized continuous production of vanadium electrolytic liquid crystals.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for cyclically preparing vanadium electrolytic liquid crystal comprises the following steps:

[0007] Step 1, dissolving VO2 with H2SO4 to obtain VOSO4 solution;

[0008] Step 2, using VOSO4 solution as the positive electrode and the negative electrode to perform electrolysis;

[0009] Step 3, heating the cathode solution to precipitate vanadium, and filtering to obtain red vanadium and filtrate A;

[0010] Step 4, adding sulfuric acid to the negative electrode solution, cooling and crystallizing, filtering to obtain V2(SO4)3*nH2O crystals and filtrate B, wherein n is selected in the range of 0-50, preferably 10-30;

[0011] Step 5, mixing red vanadium, V2(SO4)3*nH2O crystals and concentrated sulfuric acid, and solidifying and forming to obtain vanadium electrolytic liquid crystal;

[0012] Step 6: Mix filtrate A and filtrate B, adjust the valence of vanadium in the solution to +4 by adding V2O5 and / or V2O3, and add VO2 and / or H2SO4 to adjust the total vanadium and sulfate concentrations to obtain VOSO4 solution, and return the VOSO4 solution to step 2 for circulation.

[0013] Furthermore, in step 1, the usage ratio of H2SO4 to VO2 is 2.0 to 1.0, when used for the positive electrode, the usage ratio of H2SO4 to VO2 is preferably 1.5 to 1.0, and when used for the negative electrode, the usage ratio of H2SO4 to VO2 is preferably 2.0 to 1.5.

[0014] Further, in step 2, the vanadium concentration in the positive electrode VOSO4 solution is 1.25-1.75 mol / L, and the vanadium concentration in the negative electrode VOSO4 solution is 2.0-3.5 mol / L. The vanadium concentration in the positive electrode VOSO4 solution is preferably 1.5-1.75 mol / L, and the vanadium concentration in the negative electrode VOSO4 solution is preferably 2.6-3.2 mol / L.

[0015] Furthermore, the electrolysis parameters in step 2 are 50-300 mA / cm 2 , the voltage is 0.3~1.5V, and the electrolysis parameter of step 2 is preferably 150~250mA / cm 2 , the voltage is preferably 0.8~1.2V.

[0016] Furthermore, in step 2, the terminal valence state of vanadium in the positive electrode solution is +4.5 to +5.0, and the positive electrode is a (VO2)2SO4 or VOSO4 solution; the terminal valence state of vanadium in the negative electrode solution is +3.0 to +3.5, and the negative electrode is a V2(SO4)3 or VOSO4 solution.

[0017] Furthermore, in step 3, the positive electrode solution after electrolysis in step 2 is heated to a temperature of 50 to 100° C., preferably 80 to 100° C., to precipitate vanadium.

[0018] Furthermore, in step 4, sulfuric acid is added to the negative electrode solution after electrolysis in step 2 to adjust the total sulfate concentration to 6 to 12 mol / L, and the sulfate concentration is preferably 7 to 10 mol / L.

[0019] Furthermore, the temperature of cooling crystallization in step 4 is 0-30° C., and adding sulfuric acid and cooling can improve the crystallization efficiency of vanadium sulfate.

[0020] Furthermore, in step 5, red vanadium, V2(SO4)3*nH2O crystals and sulfate are reacted according to V 5+ / V 3+ The mixture is mixed at a ratio of 0.25 to 0.43 and n(S / V) of 2.4 to 2.8, and then cured and molded. 5+ / V 3+ The mixture is mixed at a ratio of 0.3 to 0.38 and n(S / V) of 2.5 to 2.7.

[0021] Furthermore, the curing molding in step 5 is performed by placing the injection mold for 6-18 hours for curing molding.

[0022] Furthermore, the concentrations of H2SO4 in step 1, step 4, and step 6 are 3.5-7.0 mol / L, 10-18.4 mol / L, and 3.5-18.4 mol / L, respectively.

[0023] Furthermore, the concentration of concentrated sulfuric acid in step 5 is 15 to 18.4 mol / L, preferably 17.5 to 18.4 mol / L.

[0024] Another object of the present invention is to disclose a vanadium electrolytic liquid crystal prepared by the above method.

[0025] Furthermore, the vanadium electrolytic liquid crystal is V2(SO4)3*nH2O*mH2SO4 and VOSO4*xH2O*yH2SO4, wherein n is 10-30, x is 0-10, m is 0-6, and y is 0-6.

[0026] Furthermore, the average valence of vanadium in the vanadium electrolytic liquid crystal is 3.5.

[0027] The vanadium electrolytic liquid crystal and the cyclic preparation method thereof of the present invention have the following advantages compared with the prior art:

[0028] 1) The method for preparing vanadium electrolytic liquid crystal in a cycle according to the present invention makes full use of the valence difference of vanadium at the positive and negative electrodes to 5+ The positive electrode filtrate contains V 3+ The negative electrode filtrate of ions reacts to produce V 4+ The ionized VOSO4 solution reduces the input of VO2 during the circulation process and saves the electrical energy consumption of VO2 production.

[0029] V 5+ +V 3+ →2V 4+ , room temperature reaction

[0030] NH3VO4+reducing agent→VO2, calcination temperature 600~800℃

[0031] 2) The method of the present invention uses only vanadium oxide and concentrated sulfuric acid as raw materials, thus avoiding the input of auxiliary materials, reducing the introduction of impurities while reducing costs, and ensuring the quality of the product to the greatest extent.

[0032] 3) The method of the present invention has simple, scientific, reasonable and pollution-free steps, and can realize the industrialized continuous production of vanadium electrolytic liquid crystals.

[0033] 4) The vanadium electrolytic liquid crystal of the present invention has few impurities, fast dissolution speed, is easy to package and transport, is suitable for the implementation of energy storage projects in remote areas, and effectively reduces project development and operation costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Process flow chart for cyclic preparation of vanadium electrolytic liquid crystals;

[0035] Figure 2 is the XRD pattern of vanadium electrolytic liquid crystal;

[0036] Figure 3 This is the cycle curve of the electrochemical performance of vanadium electrolyte. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with embodiments:

[0038] Example 1

[0039] This embodiment discloses a method for cyclically preparing vanadium electrolytic liquid crystals, such as Figure 1 As shown, the following steps are included:

[0040] (1) using sulfuric acid to dissolve VO2 at n(S / V) = 1.5, preparing 2L of positive electrode vanadyl sulfate solution with a vanadium concentration of 1.6 mol / L and 1L of negative electrode vanadyl sulfate solution with a vanadium concentration of 3.2 mol / L;

[0041] (2) After electrolysis, the valence of the positive electrode solution is 4.8, and the valence of the negative electrode solution is 3.2;

[0042] (3) The cathode solution is heated at 70°C to precipitate vanadium to obtain red vanadium and filtrate A;

[0043] (4) The negative electrode solution was heated to 20°C, and sulfuric acid was added to adjust the sulfate concentration to 10 mol / L to obtain V2(SO4)3*12H2O crystals and filtrate B;

[0044] (5) Mix red vanadium, V2(SO4)3*12H2O crystals and concentrated sulfuric acid according to V 5+ / V 3+The ratio is 0.33, n(S / V) is 0.26, and the mixture is placed in the injection mold for 12 hours to cure.

[0045] (6) Filtrate A and filtrate B are mixed, V2O3 is added to adjust the vanadium valence to +4, concentrated sulfuric acid and VO2 are added to adjust the concentration to 2L positive electrode vanadium oxysulfate solution with a vanadium concentration of 1.6 mol / L, and 1L negative electrode vanadium oxysulfate solution with a vanadium concentration of 3.2 mol / L, and the cycle is continued in step 2;

[0046] The vanadium electrolytic liquid crystal after solidification in step 5 is subjected to XRD test. Figure 2 ;

[0047] After the solidified vanadium electrolyte liquid crystal in step 5 is dissolved, it is injected into the positive and negative electrode storage tanks of the vanadium battery respectively. A 5W single-cell battery and a Xinwei 5V-6A charging and discharging device are used to perform a charge and discharge cycle test on the battery in constant current charging, constant voltage charging, and constant current discharging modes. The test results are as follows: Figure 3 .

[0048] like Figure 2 and Figure 3 It can be seen that the vanadium electrolytic liquid crystal is a mixture of V2(SO4)3*12H2O*2.75H2SO4 and VOSO4*7H2O*1.375H2SO4; after the vanadium electrolytic liquid crystal is dissolved, after 2000 cycle tests, the energy efficiency remains above 80%.

[0049] Example 2

[0050] This embodiment discloses a method for cyclically preparing vanadium electrolytic liquid crystals, such as Figure 1 As shown, the following steps are included:

[0051] (1) using sulfuric acid to dissolve VO2 at n(S / V) = 1.5 to prepare 1L of positive electrode vanadyl sulfate solution with a vanadium concentration of 1.7 mol / L and 1L of negative electrode vanadyl sulfate solution with a vanadium concentration of 2.0 mol / L;

[0052] (2) After electrolysis, the valence of the positive electrode solution is 4.9, and the valence of the negative electrode solution is 3.23;

[0053] (3) The cathode solution is heated at 95°C to precipitate vanadium to obtain red vanadium and filtrate A;

[0054] (4) The negative electrode solution was heated to 10°C, and sulfuric acid was added to adjust the sulfate concentration to 6 mol / L to obtain V2(SO4)3*nH2O crystals and filtrate B;

[0055] (5) Red vanadium, V2(SO4)3*nH2O crystals and concentrated sulfuric acid were mixed at V 5+ / V 3+The mixture was mixed with a ratio of 0.40 and n(S / V) of 0.24, and then placed in the injection mold for 12 hours to cure;

[0056] (6) Filtrate A and filtrate B are mixed, V2O5 is added to adjust the vanadium valence to +4, concentrated sulfuric acid and VO2 are added to adjust the concentration to 1L positive electrode vanadium oxysulfate solution with a vanadium concentration of 1.7 mol / L, and 1L negative electrode vanadium oxysulfate solution with a vanadium concentration of 2.0 mol / L, and return to step 2 to continue the cycle.

[0057] The vanadium electrolytic liquid crystal is dissolved in water, the concentration is adjusted to 1.65 mol / L, and injected into the positive and negative electrode storage tanks of the vanadium battery, which can be used for electrochemical energy storage.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for cyclically preparing vanadium electrolytic liquid crystals, characterized in that: The following steps are involved: Step 1, dissolving VO2 with H2SO4 to obtain VOSO4 solution; Step 2, using VOSO4 solution as the positive electrode and the negative electrode to perform electrolysis; Step 3, heating the cathode solution to precipitate vanadium, and filtering to obtain red vanadium and filtrate A; Step 4, adding sulfuric acid to the negative electrode solution, cooling and crystallizing, filtering to obtain V2(SO4)3*nH2O crystals and filtrate B, wherein n is selected in the range of 0-50; Step 5, mixing red vanadium, V2(SO4)3*nH2O crystals and concentrated sulfuric acid, and solidifying and forming to obtain vanadium electrolytic liquid crystal; Step 6: Mix filtrate A and filtrate B, adjust the valence of vanadium in the solution by adding V2O5 and / or V2O3, and adjust the total vanadium and sulfate concentrations by adding VO2 and / or H2SO4 to obtain VOSO4 solution, and return the VOSO4 solution to step 2 for circulation.

2. The method for cyclically preparing vanadium electrolytic liquid crystal according to claim 1, characterized in that: The amount of H2SO4 and VO2 used in step 1, n(S / V)=2.0~1.

0.

3. The method for cyclically preparing vanadium electrolytic liquid crystal according to claim 1, characterized in that: In step 2, the vanadium concentration in the negative electrode VOSO4 solution is 2.0~3.5mol / L, and the vanadium concentration in the positive electrode VOSO4 solution is 1.25~1.75mol / L.

4. The method for cyclically preparing vanadium electrolytic liquid crystal according to claim 1, characterized in that: Step 2: Electrolysis parameters are 50~300mA / cm 2 , the voltage is 0.3~1.5V.

5. The method for cyclically preparing vanadium electrolytic liquid crystal according to claim 1, characterized in that: In step 2, the terminal valence state of vanadium in the positive electrode solution is +4.5~+5.0, and the positive electrode is (VO2)2SO4 or VOSO4 solution; the terminal valence state of vanadium in the negative electrode solution is +3.0~+3.5, and the negative electrode is V2(SO4)3 or VOSO4 solution.

6. The method for cyclically preparing vanadium electrolytic liquid crystals according to claim 1, characterized in that: Step 3: The temperature of heating the vanadium deposition is 50-100°C.

7. The method for cyclically preparing vanadium electrolytic liquid crystals according to claim 1, characterized in that: Step 4: Add sulfuric acid to adjust the total sulfate concentration to 6-12 mol / L.

8. The method for cyclically preparing vanadium electrolytic liquid crystals according to claim 1, characterized in that: In step 5, red vanadium, V2(SO4)3*nH2O crystals and sulfate are added according to V 5+ / V 3+ The mixture is mixed in a ratio of 0.25 to 0.43 and n(S / V) of 2.4 to 2.

8.

9. A vanadium electrolytic liquid crystal, characterized in that: The method is prepared by any one of claims 1 to 8.

10. The vanadium electrolytic liquid crystal according to claim 9, characterized in that: The average valence of vanadium in vanadium electrolytic liquid crystal is 3.5.

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