CN111200153A

CN111200153A - All-vanadium redox flow battery electrolyte formula and process for inhibiting precipitation of easily precipitated element impurities of electrolyte

Info

Publication number: CN111200153A
Application number: CN201811378607.8A
Authority: CN
Inventors: 邹毅; 高新亮; 赵叶龙; 王晓丽; 陈彦博; 宋玉波; 杜新雨; 王芳; 王子; 张华民
Original assignee: Dalian Rongke Power Co Ltd
Current assignee: Dalian Rongke Power Co Ltd
Priority date: 2018-11-19
Filing date: 2018-11-19
Publication date: 2020-05-26

Abstract

本发明属于抑制电解液易沉淀元素析出领域，公开了一种用于抑制电解液易沉淀元素杂质析出的全钒液流电池电解液配方及工艺。根据易沉淀元素不同的沉淀特性和沉淀条件，综合考虑其在钒电解液中、电池中电极可承受的最高限值，将其按某一主族(或副族)同时存在或单个存在时的浓度上限进行控制，给出系统长时间安全运行的浓度区间。本发明可以有效控制易沉淀元素含量，提高电解液稳定性，延长电池电阻等设备的使用寿命，有效降低电解液成本。The invention belongs to the field of inhibiting the precipitation of easily precipitable elements in the electrolyte, and discloses an all-vanadium redox flow battery electrolyte formula and process for inhibiting the precipitation of easily precipitable elements in the electrolyte. According to the different precipitation characteristics and precipitation conditions of the easy-to-precipitate elements, comprehensively consider the maximum limit that the electrode can withstand in the vanadium electrolyte and the battery, and classify them according to a certain main group (or subgroup) when they exist at the same time or when they exist singly. The upper limit of concentration is controlled, and the concentration range for the system to operate safely for a long time is given. The invention can effectively control the content of easily precipitated elements, improve the stability of the electrolyte, prolong the service life of equipment such as battery resistance, and effectively reduce the cost of the electrolyte.

Description

All-vanadium redox flow battery electrolyte formula and process for inhibiting precipitation of easily precipitated element impurities of electrolyte

Technical Field

The invention belongs to the field of inhibiting precipitation of easily precipitated elements of electrolyte, and particularly relates to a formula and a process of all-vanadium redox flow battery electrolyte for inhibiting precipitation of easily precipitated element impurities of the electrolyte.

Background

In the existing quality standard of the electrolyte of the all-vanadium redox flow battery, the requirement on impurity metal ions in the electrolyte is single, namely the content of other elements except the main element vanadium (V) is kept in an extremely low range, but the quality standard of the electrolyte lacks the recognition and limit standard of easily precipitated elements. Part of element ions have the characteristics of easy hydrolysis, small solubility, co-ion precipitation and the like, when the element ions exist in the vanadium electrolyte, the element ions can be combined into insoluble simple substances, oxides or salts under certain conditions, and the insoluble substances are used as crystal nuclei to further promote precipitation of vanadium ions with valence of 4 and 5 and vanadium ions with valence of 2 and 3. After the sediment blocks the pipeline flow passage, the difference of the update speed of the anode solution and the cathode solution can cause the unbalance of the charge amount of the cathode electrolyte, so that the self-discharge of the battery system is aggravated, and the discharge capacity is gradually reduced.

Meanwhile, the control and detection modes of part of elements are deficient, the elements are often difficult to remove once entering the electrolyte, and the continuous accumulation characteristic of the elements causes great influence on the system capacity and efficiency, which is one of the main reasons that the flow of a plurality of vanadium battery systems is suddenly reduced, and the discharge capacity is rapidly reduced. From the practical application perspective, the allowable upper limit of the concentration of the elements in the electrolyte is not reported in relevant applications, and qualitative and quantitative descriptions are not provided; in addition, the existing all-vanadium electrolyte requires high purity (> 98%) of the raw material vanadium, and further causes the cost of the electrolyte to be high.

However, excessive limitation of the content of these elements directly increases the production cost of the electrolyte and the procurement cost of vanadium as raw material, for example, in some reports, if the content of elements such as Na, K, Al and the like is limited below 20mg/L, and if the content of elements such as Cu, Sb and the like is limited below 1mg/L, then the vanadium as raw material required for producing the electrolyte has to be used as raw material with purity of > 98%, so that the procurement cost of the raw material is increased by about 15% compared with the vanadium as raw material with purity of 97%.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides the electrolyte formula and the process of the all-vanadium redox flow battery for inhibiting the precipitation of the easily precipitated element impurities of the electrolyte, which can effectively control the content of the easily precipitated element, improve the stability of the electrolyte, prolong the service life of equipment such as battery resistance and the like, and effectively reduce the cost of the electrolyte.

The above purpose of the invention is realized by the following technical scheme:

the highest limit value of easily precipitated elements which can be borne by electrodes in the vanadium electrolyte and the battery is considered, the easily precipitated elements are controlled according to the upper limit value of the concentration of the easily precipitated elements when a certain main group (or a sub group) exists simultaneously or singly, and the concentration interval of the system for long-time safe operation is given.

The requirements for the electrolyte system are as follows:

sulfuric acid system electrolyte parameters: unless otherwise specified, the concentration of free sulfuric acid is more than 1mol/L and less than 4mol/L, and the concentration of vanadium ions is more than 1mol/L and less than 3 mol/L;

HCl system electrolyte parameters: unless otherwise specified, the concentration of free hydrochloric acid is more than 5mol/L and less than 11mol/L, and the concentration of vanadium ions is more than 2mol/L and less than 4 mol/L;

electrolyte parameters of the mixed acid system: unless otherwise specified, the concentration of free hydrochloric acid is 5mol/L or more and 11mol/L or less, the concentration of vanadium ions is 2mol/L or more and 4mol/L or less, and the concentration of free sulfuric acid is 0.1mol/L or more and 3mol/L or less;

limiting the content of hydrogen evolution elements in the raw material vanadium, wherein the content limit value is as follows: when the vanadium raw material containing the hydrogen evolution element is completely dissolved to form the electrolyte, the content of the hydrogen evolution ions of the vanadium raw material can meet the following requirements:

containing any one or more than one of the following sub-group elements 1) to 9), when each group element is present alone, it should satisfy:

the content unit of the listed elements is as follows: mg/L.m³/m²The specific meaning of the unit is as follows: ion concentration mg-L x amount of electrolyte m³Area of electrode m²(ii) a The specific content ranges are as follows:

1) main group IIA: comprises Be, Mg, Ca, Sr and Ba, wherein any element is less than or equal to 60, and Be + Mg + Ca + Sr + Ba is less than or equal to 300;

2) group IIIA: comprises B, Al and Ga, wherein any element is less than or equal to 100, and B + Al + Ga is less than or equal to 300;

3) main group IVA: comprises C, Si, Ge, Sn and Pb, wherein any element is less than or equal to 20, and C + Si + Ge + Sn + Pb is less than or equal to 100;

4) VIA main family: comprises S, Se and Te, wherein any element is less than or equal to 20, and S + Se + Te is less than or equal to 60;

5) group IIB: comprises Zn, Cd and Hg, wherein any element is less than or equal to 30, and Zn + Cd + Hg is less than or equal to 100;

6) subgroup IVB: comprises Ti and Zr, wherein any element is less than or equal to 80, and Ti + Zr is less than or equal to 160;

7) main group VA: comprises As, Sb and Bi, wherein any element is less than or equal to 10, and As + Sb + Bi is less than or equal to 30;

8) group IB: comprises Cu, Ag and Au, wherein any element is less than or equal to 10, and Cu + Ag + Au is less than or equal to 30;

9) group VIB: comprises W, Mo and Cr, wherein any one element of the W, the Mo and the Cr is 20, and the sum of W, the Mo and the Cr is less than or equal to 60;

the electrolyte is any one of the parameters of sulfuric acid system electrolyte and HCl system electrolyte and the mixed acid system electrolyte.

Further, when group IIA, group IIIA and group IVA elements are present simultaneously, the following requirements should be satisfied: be + Mg + Ca + Sr + Ba + B + Al + Ga + C + Si + Ge + Sn + Pb is less than or equal to 1000, and any element in the IIA group is less than or equal to 80, any element in the IIIA group is less than or equal to 150, and any element in the IVA group is less than or equal to 30;

further, when the elements of main group IIIA, IVB and VIB are present simultaneously, the following requirements should be met: b + Al + Ga + Ti + Zr + W + Mo + Cr is less than or equal to 700, any element in the IIIA main group is less than or equal to 100, any element in the IVB group is less than or equal to 120, and any element in the VIB group is less than or equal to 50;

further, when elements of group IIB, group VA and group IB are simultaneously present, the following requirements should be satisfied: zn + Cd + Hg + As + Sb + Bi + Cu + Ag + Au is less than or equal to 300, any element in the IIB group is less than or equal to 80, and any element in the VA main group is less than or equal to 10; any element in IB group is less than or equal to 10;

further, when the elements of main group IIA, IIB and VIA exist simultaneously, the following requirements should be satisfied: be + Mg + Ca + Sr + Ba + Zn + Cd + Hg + S + Se + Te is less than or equal to 700, and any element in IIA main group is less than or equal to 80, any element in VIA main group is less than or equal to 40, and any element in IIB main group is less than or equal to 50;

further, when the elements of main group IIA, IIIA and IVA are present simultaneously, the following requirements should be satisfied: be + Mg + Ca + Sr + Ba + B + Al + Ca + C + Si + Ge + Sn + Pb is less than or equal to 900, and any element in the IIA main group is less than or equal to 80, any element in the IVA main group is less than or equal to 30, and any element in the IIIA main group is less than or equal to 100;

The specific operation is as follows: if 2mol/L vanadium electrolyte needs to be prepared, 95 percent of V is needed₂O₅187.63g of vanadium raw material, but when the raw material contained 1.62% sodium sulfate, the raw material was completely dissolved to form a vanadium electrolyte solution containing Na⁺1000mg/L, so if the electrolyte product Na is controlled⁺<1000mg/L, the raw material with the sodium sulfate content of less than 1.62 percent is selected.

The process control method of the invention is as shown in figure 1, the raw materials are adjusted and prepared according to the process control method, and vanadium electrolyte is prepared on the basis of the element content required by the formula;

the production process of the electrolyte is divided into the following two methods: calcination reduction and electrolysis, and chemical reduction and electrolysis.

(I) calcination reduction + electrolysis method

(1) According to the standard of the amplified element content in the technical scheme of the invention, the raw material of ammonium metavanadate with vanadium purity of 95% is selected.

(2) Adding ammonium metavanadate as raw material into a reaction furnace, and adding reducing substance (NH)₃) Calcining at the high temperature of 500-900 ℃ for reduction reaction, wherein the product is vanadium (V) tetraoxide₂O₄) Powder, water, nitrogen, etc. and through cooling the reaction material inside the furnace to below 50 deg.c, the first washing and reaction of the reaction productFiltering to remove insoluble silt or washing off part of soluble salts (controlling the aperture of filter bag)<10 μm, so that insoluble substances in the process are hung in the filter bag);

(3)V₂O₄adding the powder into an acid-proof reaction kettle containing 10-15 wt% sulfuric acid or 20-25 wt% hydrochloric acid, mixing, heating, stirring, reacting for about 30 min, filtering for the second time to obtain VOSO containing 10 wt% sulfuric acid₄Or VOCl with the hydrochloric acid concentration of 25-30 wt%₂A vanadium oxychloride aqueous solution;

(4) the prepared electrolyte with the valence of 4 or more than 3.5 is pumped into a negative storage tank of an electrolysis system, and the electrolysis current (80 mA/cm) is set²) Carrying out electrolytic reduction to obtain a sulfuric acid or hydrochloric acid electrolyte finished product with a valence state of 3.5 (the vanadium ions with the valence of 3 and 4 respectively account for 50% of molar concentration).

The process of adding complexing agent or precipitant to remove impurity ions is omitted in the conventional process (because a certain amount of impurity ions are allowed to exist according to the process requirement).

(II) when the vanadium raw material is powdery V₂O₅The chemical reduction and electrolysis method is used, and the method comprises the following steps:

1) the raw material ammonium metavanadate is selected as the raw material with the vanadium purity of 95 percent according to the standard of amplified element content in the technical scheme of the invention.

2) According to the requirement of vanadium concentration in the finished product, the vanadium concentration is changed to V₂O₅Adding 10-15% sulfuric acid or 20-25% hydrochloric acid into the material, stirring to partially dissolve, and stirring for 60 min;

3) according to the ratio of 5-valent vanadium ion (VO)₂ ⁺) Is completely reduced into (VO)²⁺) The required amount of reducing agent is calculated and added with reducing agents such as oxalic acid, ethanol, saccharides and the like (SO can be directly introduced)₂Gas), making the partially dissolved 5-valent vanadium ions (VO) in the step 1)₂ ⁺) Reduced to 4-valent vanadium ions (VO)²⁺) And finally promote V₂O₅All dissolve and reduce into 4-valent vanadium ions (VO)²⁺)；

4) Filtering to remove insoluble substances (such as silt), and reducingVanadium ion (VO) of valence 4²⁺) Introducing the solution into a cathode storage tank of an electrolysis system for electrolytic reduction, and setting the electrolytic current density to be 80mA/cm according to the electrode area of the electrolysis system²Until the cathode electrolyte reaches 3.5 (the vanadium ions with 3 valence and 4 valence respectively account for 50% of molar concentration);

5) and filtering again (controlling the aperture of the filter bag to be less than 10 mu m, so that insoluble substances in the process are hung in the filter bag) to remove insoluble impurities (scraps, polymers and the like) in the solution to obtain a finished product of sulfuric acid or hydrochloric acid electrolyte.

The process of adding complexing agent or precipitator to remove impurities from impurity ions in the common process is omitted in the process (because a certain amount of impurity ions are allowed to exist according to the process requirement);

the electrolyte systems of the two methods are a sulfuric acid system and a hydrochloric acid system or a mixed acid system, wherein the sulfuric acid system is as follows: the concentration of free sulfuric acid is 1-4 mol/L, and the concentration of vanadium ions is 1-3 mol/L; hydrochloric acid system: the concentration of the free hydrochloric acid is 5-11 mol/L, and the concentration of vanadium ions is 2-4 mol/L; sulfuric acid and hydrochloric acid mixed system: the concentration of free hydrochloric acid is 5-11 mol/L, the concentration of free sulfuric acid is 0.1-3 mol/L, and the concentration of vanadium ions is 2-4 mol/L.

Compared with the prior art, the invention has the beneficial effects that:

1. reduced raw material and production costs

The excessive limitation of the content of the elements directly leads to the increase of the production cost of the electrolyte and the purchase cost of the vanadium raw material, and after the elements are released, the purchase cost of the vanadium raw material (the vanadium content is 96 percent) is reduced by about 10 percent compared with the vanadium raw material (the vanadium content has the purity of more than 98 percent) required by the prior art.

2. Interaction reduces the possibility of precipitation

In the invention, under the coexistence of other different group element ions, the influence of the precipitation of the easily precipitated element is weakened due to the interaction among the ions, and the precipitation time of the easily precipitated ion is prolonged when a plurality of ions coexist compared with the precipitation time when the ions exist independently, so that the upper limit of the concentration of the required ions for forming the precipitate in the electrolyte is improved, and finally, the maximum allowable amount of the easily precipitated metal ions in the raw material vanadium is widened, thereby reducing the precipitation.

3. The stability of the electrolyte is improved; the increase percentage of the internal resistance of the electrolyte galvanic pile is less than or equal to the increase percentage of the internal resistance of the electrolyte galvanic pile of a reference sample; under the operating condition of 45 ℃, the electrolyte of the invention has no precipitation phenomenon, and compared with the electrolyte, the precipitation phenomenon appears to block pipelines;

4. the invention allows certain easily deposited elements to exist in certain concentration, and can reduce the overall cost of the electrolyte on the basis of not influencing the performance of the solution and the battery material;

5. the content of easily precipitated elements can be effectively controlled, the stability of the electrolyte is improved, the service life of equipment such as battery resistance is prolonged, and the cost of the electrolyte is effectively reduced.

Drawings

FIG. 1 is a flow chart of the calcination reduction electrolysis process control of the present invention.

FIG. 2 is a graph comparing the operating voltage efficiency of the experimental electrolyte and the control sample in example 2 of the present invention.

Detailed Description

The invention is described in more detail below with reference to specific examples, without limiting the scope of the invention. Unless otherwise specified, the experimental methods adopted by the invention are all conventional methods, and experimental equipment, materials, reagents and the like used in the experimental method can be obtained from commercial sources.

Example 1

Vanadium electrolytes were prepared and run according to the contents of the experimental and control samples in the following table, with the results shown in the following table:

the data and the operation result show that the concentration of the above 9 types of easily-deposited elements is properly amplified and then H is adopted₂SO₄The system electrolyte, 2kW battery, experiences more than 190 charge-discharge cycles, and the experimental electrolyte system has no obvious change in system efficiency compared with the high-purity vanadium sample battery, which shows that the easily deposited elements are properly released, and the discharge capacity, efficiency and the like of the system in long-term charge-discharge operation are not affected.

Example 2

the above data and operating results show that H is used₂SO₄The system electrolyte, 2kW battery, experiences more than 190 charge-discharge cycles, and the experimental electrolyte obtained by properly amplifying the concentration of the above 9 types of easily-deposited elements maintains good efficiency compared with the electrolyte battery of a sample with higher concentration of the contrast deposited elements, has no obvious change in flow, obviously increases the system internal resistance of the contrast electrolyte, and shows that the easily-deposited elements are excessively released, and the discharge capacity and efficiency of the system are seriously influenced by long-term charge-discharge operation.

Example 3

the data and the operation results show that the concentration of the easily deposited elements in the 3 groups is properly amplified and then H is adopted₂SO₄The system electrolyte, 10kW battery, experiences more than 190 charge-discharge cycles, and the experimental electrolyte system has 6 points higher system efficiency (figure 2) than the control sample battery, which indicates that the easily deposited elements are excessively released, and the system has serious influence on the discharge capacity, efficiency and the like during long-term charge-discharge operation.

Example 4

the data and the operation results show that the concentration of the easily deposited elements in the 3 groups is properly amplified and then H is adopted₂SO₄The system electrolyte, 10kW battery, experiences more than 190 charge-discharge cycles, and the experimental electrolyte system is 6 percentage points lower than the system internal resistance of the control sample battery, which indicates that the easily deposited elements are excessively released, and the influence on the discharge capacity, efficiency and the like of the system in long-term charge-discharge operation is serious.

Example 5

the data and the operation results show that after the concentration of the easily-deposited elements in the 3 groups is properly amplified, the HCl system electrolyte and the 30kW battery are adopted, more than 190 charge-discharge cycles are carried out, and compared with a control sample battery, the experimental electrolyte system has the advantages that the system internal resistance is lower by 4.5 percent, and the voltage efficiency is higher by 4 percent. The method shows that the easily deposited elements are properly controlled, and the discharge capacity, the efficiency and the like of the system in long-term charge-discharge operation are not influenced.

Example 6

the data and the operation results show that the concentration of the easily deposited elements in the 3 groups is properly amplified and then H is adopted₂SO₄The system electrolyte, 30kW battery, undergoes more than 190 charge-discharge cycles, and compared with the control sample battery, the experimental electrolyte system has both system internal resistance and voltage efficiencyElectrolyte solution due to control sample. The method shows that the easily deposited elements are properly controlled, and the discharge capacity, the efficiency and the like of the system in long-term charge-discharge operation are well maintained.

Example 7

the above data and operating results show that, properly scaling up the concentration of the group 3 easily depositable element above, the concentration limit of the element is reduced due to interaction. Experiment adopted H₂SO₄The system electrolyte, 30kW battery, experiences more than 190 charge-discharge cycles, and the experimental electrolyte system is inferior to the experimental electrolyte in both internal resistance and voltage efficiency compared with the control sample battery. The method shows that the easily deposited elements are excessively amplified, and the influence on the discharge capacity, the efficiency and the like of the system in long-term charge-discharge operation is serious.

Example 8

the above data and operating results show that, properly scaling up the concentration of the group 3 easily depositable element above, the concentration limit of the element is reduced due to interaction. The experiment adopts HCl system electrolyte, 10kW battery, experiences more than 190 charge-discharge cycles, and the internal resistance and voltage efficiency of the control experiment system are inferior to those of the experiment electrolyte compared with the control sample battery. The method shows that the easily deposited elements are excessively amplified, and the influence on the discharge capacity, the efficiency and the like of the system in long-term charge-discharge operation is serious.

Example 9

the above data and operating results show that the concentrations of the above group 3 easily depositable elements are properly amplified. The experiment adopts mixed acid system electrolyte, and a 30kW battery undergoes more than 190 charge-discharge cycles, and compared with a control high-purity vanadium sample battery, the experiment electrolyte system has no obvious difference in system internal resistance and voltage efficiency. The method shows that the easily deposited elements are properly amplified, and the discharge capacity, the efficiency and the like of the system in long-term charge-discharge operation are not influenced.

During continuous experiments, the content of the elements is properly released to a certain range, so that the system is ensured not to precipitate, the purchasing difficulty is reduced on the basis of not influencing the performance of the battery, the purity of the raw material is reduced to about 96% from more than 98%, and the cost of the raw material is reduced by 10%.

Experiments also find that if the easily precipitated elements coexist in other element ions, the precipitation influence of some easily precipitated elements is weakened due to the interaction among the ions, the precipitation possibility of the independently existing element ions is reduced due to the existence of multiple ions, the upper limit of the concentration of the required ions for forming precipitates in the electrolyte is improved, and the maximum allowable amount of the easily precipitated metal ions in the final raw material vanadium is widened.

Further, the pore size of the large filter bag is controlled, so that substances which are easy to deposit in the electrolyte of the system can be deposited in the filter bags of the positive electrode and the negative electrode of the system, the influence of the substances on the pipelines and the battery of the system can be greatly reduced, and the content of the elements which are easy to deposit can be further widened.

Compared with the prior art, the invention

1. Reduced raw material and production costs

Over-limiting the content of these elements will directly lead to an increase in the electrolyte production cost and in the raw material vanadium procurement cost:

the specific results are as follows:

data in the table, the average conversion is mg/L calculation

After the elements are released, the cost of the raw materials (vanadium content is 96%) needed to be purchased is reduced by about 15% compared with the vanadium (vanadium content purity is more than 98%) needed in the patent CN 105283996A.

2. Interaction reduces the possibility of precipitation

The upper limit of the element content is shown in the following table

Data in the table are converted into mg/L

3. The stability of the electrolyte is improved;

the specific results are as follows:

the increase percentage of the internal resistance of the electrolyte galvanic pile is less than or equal to the increase percentage of the internal resistance of the electrolyte galvanic pile of a reference sample; under the operating condition of 45 ℃, the electrolyte of the invention has no precipitation phenomenon, and compared with the electrolyte, the electrolyte has precipitation to block pipelines.

The embodiments described above are merely preferred embodiments of the invention, rather than all possible embodiments of the invention. Any obvious modifications to the above would be obvious to those of ordinary skill in the art, but would not bring the invention so modified beyond the spirit and scope of the present invention.

Claims

1. an all-vanadium redox flow battery electrolyte formula that is used to suppress the easy precipitation element impurities of the electrolyte to separate out, it is characterized in that, in the raw material vanadium, the content of hydrogen-evolution element is limited, and its content limit is: when containing the hydrogen-evolved element vanadium raw material After being completely dissolved to form an electrolyte, the hydrogen evolution ion content should meet:

Contains any one or more of the subgroup elements in the following 1)-9), when each element exists alone, it should satisfy:

1) IIA main group: including Be, Mg, Ca, Sr, Ba, and any one of them ≤ 60, Be+Mg+Ca+Sr+Ba≤300;

2) IIIA main group: including B, Al, Ga, and any element of them≤100, B+Al+Ga≤300;

3) IVA main group: including C, Si, Ge, Sn, Pb, and any one of the elements ≤ 20, C+Si+Ge+Sn+Pb≤100;

4) VIA main group: including S, Se, Te, and any one of them is ≤20, S+Se+Te≤60;

5) IIB subgroup: including Zn, Cd, Hg, and any one of them is less than or equal to 30, and Zn+Cd+Hg is less than or equal to 100;

6) IVB subgroup: including Ti and Zr, and any element of them is less than or equal to 80, and Ti+Zr is less than or equal to 160;

7) VA main group: including As, Sb, Bi, and any element of them≤10, As+Sb+Bi≤30;

8) IB subgroup: including Cu, Ag, Au, and any element of them≤10, Cu+Ag+Au≤30;

9) VIB subgroup: including W, Mo, Cr, and any element of them is 20, W+Mo+Cr≤60;

The unit of element content listed above is: mg/L·m ³ /m ² The specific meaning of the unit is: ion concentration mg/L × electrolyte amount m ³ /electrode area m ² ;

The electrolyte system is any one of the parameters of the sulfuric acid system electrolyte, the HCl system electrolyte and the mixed acid system electrolyte thereof.

2. a kind of all-vanadium redox flow battery electrolyte formula for suppressing the precipitation element impurities of the electrolyte solution according to claim 1, it is characterized in that, the easy precipitation elements exist simultaneously by a certain main group or subgroup and The upper limit of the concentration when a single exists is controlled, and the concentration range for the system to operate safely for a long time is given; the electrolyte system requirements are as follows:

(1) Sulfuric acid system electrolyte parameters: free sulfuric acid concentration is more than 1mol/L and less than 4mol/L, and vanadium ion concentration is more than 1mol/L and less than 3mol/L;

(2) HCl system electrolyte parameters: free hydrochloric acid concentration is more than 5mol/L and less than 11mol/L, and vanadium ion concentration is more than 2mol/L and less than 4mol/L;

(3) Electrolyte parameters of mixed acid system: free hydrochloric acid concentration is above 5mol/L and below 11mol/L, vanadium ion concentration is above 2mol/L and below 4mol/L, free sulfuric acid concentration is above 0.1mol/L and 3mol/L the following.

3. a kind of all-vanadium redox flow battery electrolyte formula for suppressing the easy precipitation element impurity of electrolyte to separate out according to claim 1 is characterized in that, when IIA group, IIIA group and IVA group element exist simultaneously, should be. Meet the following requirements: Be+Mg+Ca+Sr+Ba+B+Al+Ga+C+Si+Ge+Sn+Pb≤1000, and any element of group IIA≤80, any element of group IIIA≤150 , any element in the IVA group ≤ 30, the unit of the above-listed element content is: mg/L·m ³ /m ² The specific meaning of the unit is: ion concentration mg/L × electrolyte amount m ³ /electrode area m ² .

4. a kind of all-vanadium redox flow battery electrolyte formula for suppressing the easy precipitation element impurity of electrolyte to separate out according to claim 1, is characterized in that, when IIIA main group, IVB group and VIB group element exist simultaneously, The following requirements should be met: B+Al+Ga+Ti+Zr+W+Mo+Cr≤700, and any element of IIIA main group≤100, any element of IVB group≤120, any element of VIB group≤ 50. The unit of element content listed above is: mg/L·m ³ /m ² The specific meaning of the unit is: ion concentration mg/L×electrolyte amount m ³ /electrode area m ² .

5. a kind of all-vanadium redox flow battery electrolyte formula for suppressing the precipitation of element impurities in the electrolyte according to claim 1, it is characterized in that, when IIB group, VA main group and IB group elements exist simultaneously, should Meet the following requirements: Zn+Cd+Hg+As+Sb+Bi+Cu+Ag+Au≤300, and any element of group IIB≤80, any element of VA main group≤10; any element of group IB ≤10, the unit of element content listed above is: mg/L·m ³ /m ² The specific meaning of the unit is: ion concentration mg/L×electrolyte amount m ³ /electrode area m ² .

6. a kind of all-vanadium redox flow battery electrolyte formula for suppressing the precipitation element impurities of the electrolyte solution according to claim 1, it is characterized in that, when IIA main group, IIB group and VIA main group elements exist simultaneously, The following requirements should be met: Be+Mg+Ca+Sr+Ba+Zn+Cd+Hg+S+Se+Te≤700, and any element of IIA main group≤80, any element of VIA main group≤40, Any element in the IIB main group is ≤50, and the unit of the above-listed element content is: mg/L·m ³ /m ² The specific meaning of the unit is: ion concentration mg/L×electrolyte amount m ³ /electrode area m ² .

7. a kind of all-vanadium redox flow battery electrolyte formula for suppressing the easy precipitation element impurity of electrolyte to separate out according to claim 1 is characterized in that, when IIA main group, IIIA group and IVA main group elements exist simultaneously, The following requirements should be met: Be+Mg+Ca+Sr+Ba+B+Al+Ca+C+Si+Ge+Sn+Pb≤900, and any element of IIA main group≤80, any one of IVA main group Element≤30, any element of IIIA main group≤100.

8. the technique of making all-vanadium redox flow battery electrolyte according to the formula of claim 1, is characterized in that, preparation technique adopts any in calcination reduction+electrolysis method, chemical reduction+electrolysis method.

9. technique as claimed in claim 8, is characterized in that, described calcination reduction+electrolysis concrete steps are as follows:

1) select the raw material that vanadium purity is 95%;

2) The raw material ammonium metavanadate is added to the reaction furnace, and the reducing substance NH is added to calcine at a high temperature _of 500-900 ° C, and the reduction reaction is carried out, and the products are V ₂ O ₄ powder, water, nitrogen, and the reaction material in the furnace is cooled to 50 After the temperature is below ℃, the reaction product is washed and filtered for the first time to filter out insoluble sediment or wash away part of soluble salts;

3) V ₂ O ₄ powder is added into an acid-proof reaction kettle containing sulfuric acid with a concentration of 10-15wt% or hydrochloric acid with a concentration of 20-25wt% and mixed, reacted by heating and stirring for about 30 minutes, and prepared after the second filtration. Aqueous solution containing VOSO ₄ with a sulfuric acid concentration of 10wt% or a hydrochloric acid concentration of 25-30wt% VOCl ₂ vanadium oxychloride;

4) push the prepared 4-valence or greater than 3.5-valence electrolyte into the negative electrode storage tank of the electrolysis system, set an electrolytic current 80mA/cm , carry out electrolytic reduction, and obtain a valence state of 3.5 ^- valence sulfuric acid or hydrochloric acid type electrolyte finished product.

10. technique as claimed in claim 8, is characterized in that, described chemical reduction+electrolysis concrete steps are as follows:

When the vanadium raw material is powdered V ₂ O ₅ ,

1) select the raw material that vanadium purity is 95%;

2) According to the vanadium concentration requirement in the finished product, add sulfuric acid or 20-25wt% hydrochloric acid with a concentration of 10-15wt% to the V ₂ O ₅ material and stir first to partially dissolve it, and stir for 60 minutes;

₃ ) According to the amount of reducing agent required to completely reduce VO ²⁺ to VO ²⁺ , calculate and add reducing agent to reduce the partially dissolved VO ²⁺ in step ₁ ), and finally promote the complete dissolution and reduction of V ₂ O ₅ is VO ²⁺ ;

4) By filtration, after removing the insolubles, it will be reduced to VO ²⁺ solution, passed into the cathode storage tank of the electrolysis system for electrolytic reduction, and according to the electrode area of the electrolysis system, the electrolytic current density is set to 80mA/cm ² , until the negative electrode electrolyte Reach 3.5 price;

5) Filter again to remove insoluble impurities in the solution to obtain the finished product of sulfuric acid or hydrochloric acid electrolyte.