High purity vanadium oxide electrode and method of making same

Abstract

The application belongs to the field of hydrometallurgy, and particularly discloses a high-purity vanadium oxide electrode and a preparation method thereof. The method comprises the following steps: pretreating an alkaline vanadium leaching solution by using an active alumina adsorption column to obtain a pretreated solution; adding a composite impurity removing agent mainly composed of modified lignin sulfonate to the pretreated solution for primary impurity removal to obtain a primary impurity removal filtrate; adding calcium hydroxide suspension and a flocculating agent to the primary impurity removal filtrate for secondary impurity removal to obtain a secondary impurity removal filtrate; purifying the secondary impurity removal filtrate by using an ion exchange column to obtain a purified solution; adding an ammonium salt to the purified solution for vanadium precipitation to obtain ammonium metavanadate crystals; calcining the ammonium metavanadate crystals to obtain high-purity vanadium pentoxide; and preparing the high-purity vanadium oxide electrode by using the high-purity vanadium pentoxide. According to the application, the alkaline vanadium leaching solution is used as a raw material, and the high-purity vanadium pentoxide is prepared through a multi-stage deep impurity removal process, and the high-purity vanadium oxide electrode is prepared by using the high-purity vanadium pentoxide as a raw material.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of hydrometallurgy, and particularly relates to a high-purity vanadium oxide electrode and a preparation method thereof. BACKGROUND

[0002] Vanadium pentoxide (V2O5) is an electrode material with important application value in the field of electrochemistry. The purity of vanadium pentoxide is one of the key factors affecting the electrode performance. The presence of impurities or insufficient purity will directly affect the electrochemical performance of the electrode (such as specific capacity, cycle stability, rate performance, etc.) by changing the crystal structure, electronic conductivity, ion diffusion path and chemical stability of the material.

[0003] Currently, the main method for industrial production of high-purity vanadium pentoxide is ammonium salt vanadium precipitation process, which has the following technical bottlenecks:

[0004] 1. Incomplete removal of impurities: The traditional sulfidation method for removing heavy metals produces toxic H2S gas, and the removal efficiency of iron and aluminum impurities by pH adjustment method is low (usually only reduced to 100-200 ppm), and silicon and phosphorus impurities are difficult to be removed simultaneously.

[0005] 2. Serious environmental pollution: The existing technology uses sulfuric acid to adjust the pH to 2-3 for impurity removal, which produces a large amount of ammonia-containing wastewater; and the use of phosphate precipitants easily leads to the accumulation of phosphorus elements.

[0006] 3. Complex process flow: The combined process of "solvent extraction-ion exchange" requires large equipment investment and high organic phase loss; and some technologies still need multi-stage calcination (500℃→700℃→900℃) to obtain high-purity products.

[0007] For the treatment of alkaline vanadium leaching solution (mainly composed of NaVO3, pH 9-11), the existing technology has obvious deficiencies: (1) direct acidification will release a large amount of ammonia gas; (2) the forms of impurities are complex (Na2SiO3, Na3PO4, etc.); (3) the use of magnesium salt dephosphorization agent will introduce new magnesium impurities (residual amount >300 ppm).

[0008] Therefore, there is still room for improvement in the process of preparing high-purity vanadium pentoxide from alkaline vanadium leaching solution and preparing electrodes from the same. SUMMARY

[0009] The main purpose of the present application is to solve the problems of incomplete removal of impurities, serious environmental pollution and complex process flow in the existing high-purity vanadium pentoxide preparation process, and the problems of poor performance of vanadium oxide electrodes prepared from the existing alkaline vanadium leaching solution, by providing a method for preparing high-purity vanadium pentoxide from alkaline vanadium leaching solution and preparing high-purity vanadium oxide electrodes from the same.

[0010] To achieve the above object, the present application adopts the following technical solutions:

[0011] According to a first aspect of the present application, a preparation method of a high-purity vanadium oxide electrode is provided, comprising the following steps:

[0012] S1: pretreating an alkaline vanadium leaching solution by using an active alumina adsorption column to obtain a pretreated solution;

[0013] S2: adding a composite impurity removal agent mainly composed of modified lignin sulfonate to the pretreated solution for primary impurity removal, and obtaining a primary impurity removal filtrate after solid-liquid separation;

[0014] S3: adding a calcium hydroxide suspension and a flocculating agent to the primary impurity removal filtrate for secondary impurity removal, and obtaining a secondary impurity removal filtrate after solid-liquid separation;

[0015] S4: purifying the secondary impurity removal filtrate by using an ion exchange column to obtain a purified solution;

[0016] S5: adding an ammonium salt to the purified solution for vanadium precipitation to obtain ammonium metavanadate crystals;

[0017] S6: calcining the ammonium metavanadate crystals to obtain high-purity vanadium pentoxide;

[0018] S7: preparing a high-purity vanadium oxide electrode by using the high-purity vanadium pentoxide.

[0019] According to some embodiments of the present application, step S1 comprises: passing the alkaline vanadium leaching solution through the active alumina adsorption column at a flow rate of 1-5 BV / h, with the temperature controlled at 40-60℃, to obtain the pretreated solution.

[0020] According to some embodiments of the present application, step S2 comprises: adding the composite impurity removal agent mainly composed of modified lignin sulfonate to the pretreated solution, maintaining pH 9-10, and reacting for 30-90 min under stirring, to obtain the primary impurity removal filtrate after solid-liquid separation.

[0021] According to some embodiments of the present application, step S3 comprises: heating the primary impurity removal filtrate to 60-100℃, adding the calcium hydroxide suspension and the flocculating agent, and aging for 30-60 min, to obtain the secondary impurity removal filtrate after solid-liquid separation.

[0022] According to some embodiments of the present application, step S4 comprises: passing the secondary impurity removal filtrate through the ion exchange column at a flow rate of 1.5-2 BV / h to obtain the purified solution.

[0023] According to some embodiments of the present application, step S5 comprises: adjusting the pH of the purified solution to 8-9, adding the ammonium salt, and crystallizing at 30-90 DEG C for 1-2 hours to obtain the ammonium metavanadate crystals.

[0024] According to some embodiments of the present application, step S6 comprises: segmentally calcining the ammonium metavanadate crystals in an oxygen atmosphere, first increasing to 300 DEG C at a rate of 5-10 DEG C / min and maintaining for 0.5-1.5 hours, then increasing to 550 DEG C at a rate of 2-8 DEG C / min and maintaining for 1-3 hours, to obtain the high-purity vanadium pentoxide.

[0025] According to some embodiments of the present application, the main agent of the composite impurity removal agent is an amino polysaccharide modified lignin sulfonate, and the composite impurity removal agent further comprises a citrate.

[0026] According to some embodiments of the present application, the addition amount of the composite impurity removal agent is 1.1-1.3 times the molar amount of vanadium in the basic vanadium leaching solution.

[0027] According to some embodiments of the present application, in the composite impurity removal agent, the mass ratio of lignin sulfonate, citrate, and amino polysaccharide is 5-8:2-1:1.

[0028] According to some embodiments of the present application, the composite impurity removal agent is prepared by: mixing lignin sulfonate and amino polysaccharide in a certain proportion, adding a potassium persulfate solution, and oxidizing and modifying at 60-80 DEG C for 1-3 hours to obtain an amino polysaccharide modified lignin sulfonate; and compounding the amino polysaccharide modified lignin sulfonate with a citrate to obtain the composite impurity removal agent.

[0029] According to some embodiments of the present application, the addition amount of the calcium hydroxide suspension is 2-3 times the molar amount of phosphorus in the basic vanadium leaching solution in terms of the molar amount of calcium.

[0030] According to some embodiments of the present application, the flocculant is a polyacrylamide flocculant with a mass fraction of 0.1-0.25%.

[0031] According to some embodiments of the present application, the addition amount of the ammonium salt is 2-3.5 times the molar amount of vanadium in the basic vanadium leaching solution in terms of the molar amount of NH4 + .

[0032] According to a second aspect of the present application, there is provided a high-purity vanadium oxide electrode prepared by the above method.

[0033] By using the above technical solutions, the present application has the following beneficial effects:

[0034] The scheme of the present application uses an alkaline vanadium leaching solution as raw material, and through a multi-stage deep impurity removal process, high-purity vanadium pentoxide (V2O5≥99.9%) is prepared, and a high-performance electrode is prepared using the high-purity vanadium pentoxide as raw material. Specifically, the scheme of the present application first uses an activated alumina adsorption column to pretreat the alkaline vanadium leaching solution to remove part of the silicon impurities and co-adsorbed aluminum in the alkaline vanadium leaching solution, then uses a composite impurity remover mainly composed of modified lignin sulfonate as a main agent for primary impurity removal to remove phosphorus, aluminum and residual silicon impurities, then uses calcium hydroxide and a flocculating agent for secondary impurity removal to remove part of the phosphorus, residual silicon and co-precipitated aluminum impurities, and then uses an ion exchange column for deep purification to remove part of the aluminum and silicon impurities and the calcium impurities introduced in the previous step, thereby obtaining a purified solution after deep impurity removal. After vanadium precipitation is performed on the purified solution after deep impurity removal and the ammonium metavanadate crystals obtained by vanadium precipitation are calcined, high-purity vanadium pentoxide is obtained. The high-purity vanadium oxide electrode prepared using the high-purity vanadium pentoxide has excellent specific capacity, cycle stability and rate performance.

[0035] The scheme of the present application uses an environmentally friendly impurity removal agent system to achieve efficient and simultaneous removal of silicon, phosphorus, aluminum and other impurity elements, and the impurity content in the final product is Si≤2ppm, P≤2ppm and Al≤2ppm, and the problem of ammonia-nitrogen pollution caused by traditional acid impurity removal processes is solved. The scheme of the present application avoids equipment corrosion and ammonia emission caused by the use of strong acid and strong base. The scheme of the present application simplifies the production process of existing high-purity V2O5. Compared with the traditional process, the vanadium recovery rate of the scheme of the present application is increased by more than 98.5%, and the cost of the impurity removal agent is reduced. The specific surface area of the V2O5 obtained by the scheme of the present application is 15-18 m² / g (nitrogen adsorption method), and the Na and K contents are both <2 ppm, which meets the requirements of the positive electrode material of a battery (for example, a lithium battery). BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A flowchart of the preparation method of the high-purity vanadium oxide electrode provided by the present application. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to specific examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0038] According to the needs, specific embodiments of the present application are disclosed in the specification of the present application; however, it should be understood that the embodiments disclosed herein are only examples of the present application which can be implemented in various alternative forms. In the following description, a plurality of operating parameters and components are described in a plurality of embodiments conceived. These specific parameters and components are only examples in the specification and do not mean limitation.

[0039] The first aspect of the present application provides a method for preparing a high-purity vanadium oxide electrode, as shown in the formula, which comprises the following steps: Figure 1 S1: pretreating the alkaline vanadium leaching solution by using an active alumina adsorption column to obtain a pretreated solution; S2: adding a composite impurity removal agent mainly composed of modified lignin sulfonate to the pretreated solution for primary impurity removal, and then performing solid-liquid separation to obtain a primary impurity removal filtrate; S3: adding calcium hydroxide suspension and a flocculating agent to the primary impurity removal filtrate for secondary impurity removal, and then performing solid-liquid separation to obtain a secondary impurity removal filtrate; S4: purifying the secondary impurity removal filtrate by using an ion exchange column to obtain a purified solution; S5: adding an ammonium salt to the purified solution for vanadium precipitation to obtain ammonium metavanadate crystals; S6: calcining the ammonium metavanadate crystals to obtain high-purity vanadium pentoxide; and S7: preparing a high-purity vanadium oxide electrode by using the high-purity vanadium pentoxide.

[0040] The present application uses alkaline vanadium leaching solution as raw material, and prepares high-purity vanadium pentoxide through a multi-stage deep impurity removal process, and uses the high-purity vanadium pentoxide as raw material to prepare a high-performance electrode. Specifically, first, the alkaline vanadium leaching solution is pretreated by using an active alumina adsorption column to remove part of the silicon impurities and co-adsorbed aluminum in the alkaline vanadium leaching solution, and then a composite impurity removal agent mainly composed of modified lignin sulfonate is used for primary impurity removal to remove phosphorus, aluminum and residual silicon impurities, and then calcium hydroxide and a flocculating agent are used for secondary impurity removal to remove part of the phosphorus, residual silicon and co-precipitated aluminum impurities, and then an ion exchange column is used for deep purification to remove part of the aluminum and silicon impurities and the calcium impurities introduced in the previous step, thereby obtaining a deep-impurity-removed purified solution. After vanadium precipitation is performed on the deep-impurity-removed purified solution and the ammonium metavanadate crystals obtained by the vanadium precipitation are calcined, high-purity vanadium pentoxide can be obtained. The high-purity vanadium oxide electrode prepared by using the high-purity vanadium pentoxide has excellent specific capacity, cycle stability and rate performance.

[0041] The present application uses an environmentally friendly impurity removal agent system to achieve efficient and simultaneous removal of silicon, phosphorus, aluminum and other impurity elements, and solves the ammonia nitrogen pollution problem caused by traditional acid impurity removal processes. The present application avoids equipment corrosion and ammonia emission caused by the use of strong acid and strong base. The present application simplifies the existing production process of high-purity V2O5. Compared with traditional processes, the method of the present application has the advantages of high vanadium recovery rate, low impurity removal agent cost and simple production process.

[0042] In the present application, the alkaline vanadium leaching solution refers to a vanadium-containing solution with alkalinity. The present application does not have specific requirements for the composition of the alkaline vanadium leaching solution. The method of the present application is suitable for treating alkaline vanadium leaching solutions containing silicon, phosphorus, aluminum and other impurity elements. In the examples described below, the alkaline vanadium leaching solution contains V 20-38g / L, Si 800-1200mg / L, P 300-500mg / L, Al 200-400mg / L, and pH is 9-11.

[0043] The scheme of the present application will be described in detail in combination with each step.

[0044] In step S1, the active alumina adsorption column is used to pretreat the alkaline vanadium leaching solution, aiming to remove part of the silicon impurities and co-adsorbed aluminum in the alkaline vanadium leaching solution. The active alumina adsorption column has the advantages of high silicon removal efficiency, simple operation, low cost, and strong adaptability.

[0045] The active alumina has a high specific surface area and a rich mesoporous structure (2-50 nm), and can trap colloidal silicon or polymeric silicic acid in the solution through physical adsorption, especially when the particle size of the silicon species matches the pore size. At the same time, non-dissociated silicic acid molecules (H4SiO4) can be adsorbed on the surface of the alumina through van der Waals forces.

[0046] In some embodiments, step S1 comprises passing the alkaline vanadium leaching solution through the active alumina adsorption column at a flow rate of 1-5 BV / h to obtain a pretreated solution. This flow rate range is conducive to the adsorption of silicon by the active alumina, thereby achieving excellent silicon removal effect. The flow rate of the alkaline vanadium leaching solution can typically but not limitatively be set to 1 BV / h, 2 BV / h, 3 BV / h, 4 BV / h, 5 BV / h.

[0047] In some embodiments, the temperature in step S1 is controlled to be 40-60°C. This temperature range can achieve a good balance between adsorption efficiency and energy consumption; too low a temperature will result in too slow adsorption rate, thereby affecting the adsorption efficiency; too high a temperature will increase energy consumption and may damage the structure of the active alumina. The temperature can typically but not limitatively be set to 40°C, 45°C, 50°C, 55°C, 60°C. Preferably, the temperature is controlled to be 50°C.

[0048] In some embodiments, the particle size of the active alumina in the active alumina adsorption column in step S1 is 1-2 mm.

[0049] In some embodiments, step S1 can remove about 40% of the silicon.

[0050] When the active alumina adsorption column reaches saturation in adsorption, it can be regenerated to elute the adsorbed pollutants and restore its adsorption activity, thereby achieving repeated use. The regeneration method of the active alumina adsorption column is: after reverse flushing with 5% NaOH solution, activating with 3% H2SO4, the regeneration efficiency is >95%.

[0051] In step S2, the composite impurity removal agent mainly composed of modified lignin sulfonate is added to the pretreated solution for primary impurity removal, aiming to remove part of silicon, phosphorus and aluminum impurities in the pretreated solution. The composite impurity removal agent mainly composed of modified lignin sulfonate has the advantages of remarkable impurity removal effect, wide application range and environmental friendliness, etc.

[0052] In some embodiments, the main agent of the composite impurity removal agent is amino polysaccharide modified lignin sulfonate, and the composite impurity removal agent further comprises citrate. In other words, the composite impurity removal agent is made of lignin sulfonate, citrate and amino polysaccharide.

[0053] The lignin sulfonate, citrate and amino polysaccharide can achieve efficient impurity removal through synergistic effect. The lignin sulfonate is an anionic surfactant with good dispersing performance, which can be dissolved in water of any hardness and has good chemical stability in aqueous solution and is biodegradable. It has good chelating ability for silicon, phosphorus and aluminum ions and can be used as a chelating agent to remove silicon, phosphorus and aluminum impurities in the solution. The citrate is a weak acid salt with complexation. It can form stable complexes with metal ions in the solution, thereby reducing the concentration of metal ions and achieving the purpose of impurity removal. Meanwhile, the citrate also has the function of adjusting the pH value of the solution, which helps to optimize the impurity removal environment. The amino polysaccharide is a kind of polysaccharide compound containing amino groups (-NH2) or amino derivatives (such as acetyl amino groups), which is connected by glycosidic bonds. It has the biological compatibility of polysaccharide and the chemical activity of amino group, and is a natural high molecular polymer with good adsorption and flocculation performance. It can remove silicon, phosphorus, aluminum and other impurities in the solution through adsorption, and can also make impurity particles aggregate through flocculation, which is convenient for separation. The three components cooperate with each other, the chelation of lignin sulfonate, the complexation of citrate and the adsorption and flocculation of amino polysaccharide, which can more comprehensively and efficiently remove various impurities in the solution. In addition, lignin sulfonate and amino polysaccharide are natural or naturally derived substances, and citrate is also a relatively environmentally friendly reagent, so the composite impurity removal agent has less environmental pollution compared with traditional chemical impurity removal agents.

[0054] The lignin sulfonate can be sodium lignin sulfonate, potassium lignin sulfonate, calcium lignin sulfonate, magnesium lignin sulfonate, ammonium lignin sulfonate, etc., and is preferably the corresponding sodium salt or potassium salt. The citrate can be trisodium citrate, sodium dihydrogen citrate, potassium dihydrogen citrate, ammonium dihydrogen citrate, disodium hydrogen citrate, etc., and is preferably the corresponding sodium salt or potassium salt. The amino polysaccharide can be chitosan, chitooligosaccharide, etc.

[0055] In some embodiments, the lignin sulfonate is sodium lignin sulfonate, the citrate is trisodium citrate, and the amino polysaccharide is chitosan.

[0056] In some embodiments, the amount of the composite impurity removal agent added is 1.1-1.3 times the molar amount of vanadium in the alkaline vanadium leaching solution. Here, the "amount added" refers to the total molar amount of the substances in the composite impurity removal agent, i.e., the total molar amount of the three substances of lignosulfonate, citrate, and amino polysaccharide. The amount of the composite impurity removal agent added can typically but not limitatively be set to 1.1 times, 1.2 times, or 1.3 times the molar amount of vanadium in the alkaline vanadium leaching solution.

[0057] In some embodiments, the mass ratio of the three substances of lignosulfonate, citrate, and amino polysaccharide in the composite impurity removal agent is 5-8:2-1:1. This ratio helps achieve the best impurity removal effect.

[0058] In some embodiments, the composite impurity removal agent is prepared by mixing lignosulfonate and amino polysaccharide in a certain proportion, adding a potassium persulfate solution, and oxidatively modifying at 60-80°C for 1-3 h to obtain amino polysaccharide-modified lignosulfonate. Then, the amino polysaccharide-modified lignosulfonate is compounded with citrate to obtain the composite impurity removal agent. Potassium persulfate (K2S2O8) mainly acts as a free radical initiator and oxidant to promote the chemical cross-linking and structural modification of lignosulfonate and amino polysaccharide. Thermal decomposition generates free radicals, oxidizes lignosulfonate, oxidizes amino polysaccharide, and initiates graft copolymerization. Subsequently, physical mixing of the amino polysaccharide-modified lignosulfonate and citrate is performed. The reaction temperature can typically but not limitatively be set to 60°C, 65°C, 70°C, 75°C, or 80°C, and the reaction time can typically but not limitatively be set to 1 h, 1.5 h, 2 h, 2.5 h, or 3 h.

[0059] In some embodiments, step S2 comprises adding the composite impurity removal agent to the pretreatment solution, maintaining a pH of 9-10, and reacting for 30-90 min under stirring, followed by solid-liquid separation to obtain a primary impurity removal filtrate. The pH can typically but not limitatively be adjusted to 9.0, 9.2, 9.4, 9.6, 9.8, or 10, and the reaction time can typically but not limitatively be set to 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, or 90 min.

[0060] For example, in one specific example, sodium lignosulfonate is mixed with chitosan in a certain proportion, 0.1 mol / L potassium persulfate solution is added (the amount is 20% of the solid mass in terms of the mass of potassium persulfate), oxidative modification is performed at 60-80°C for 1-3 h, and then trisodium citrate is compounded to obtain the composite impurity removal agent. The composite impurity removal agent is added to the pretreatment solution, the stirring rate is set to 200-500 rpm, a pH of 9-10 is maintained, and after reacting for 30-90 min, filtration is performed, and the obtained filtrate is a primary impurity removal filtrate.

[0061] In step S3, the calcium hydroxide suspension and the flocculant are added to the primary impurity removal filtrate for secondary impurity removal, aiming to remove part of the phosphorus impurities, residual silicon and co-precipitated aluminum impurities in the primary impurity removal filtrate. This way of impurity removal has the advantages of high impurity removal efficiency, simple operation and low cost.

[0062] The calcium hydroxide suspension and the flocculant realize the deep removal of phosphorus in the primary impurity removal filtrate through the synergistic effect of chemical precipitation and flocculation strengthening. The calcium hydroxide provides an alkaline environment and Ca 2+ , which makes phosphorus, silicon and aluminum form precipitates. The flocculant aggregates these precipitates into large particles, improving the solid-liquid separation efficiency. The co-precipitation effect makes Al(OH)3, CaSiO3 and Ca5(PO4)3OH mutually wrapped, improving the impurity removal rate.

[0063] In some embodiments, step S3 comprises: warming the primary impurity removal filtrate to 60-100°C, adding the calcium hydroxide suspension and the flocculant, aging for 30-60 min, and then obtaining the secondary impurity removal filtrate after solid-liquid separation. The reaction temperature can be typically but not limitedly set to 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, and the aging time can be typically but not limitedly set to 30 min, 40 min, 50 min or 60 min.

[0064] In some embodiments, the amount of the calcium hydroxide suspension added is 2-3 times the amount of phosphorus in the alkaline vanadium leaching solution in terms of calcium molar amount. The amount of the calcium hydroxide suspension added can be typically but not limitedly set to 2 times, 2.5 times or 3 times the amount of phosphorus in the alkaline vanadium leaching solution in terms of calcium molar amount.

[0065] In some embodiments, the flocculant is a polyacrylamide flocculant with a mass fraction of 0.1-0.25%.

[0066] For example, in a specific example, the primary impurity removal filtrate is warmed to 60-100°C, the Ca(OH)2 suspension is added to a Ca / P molar ratio of 2-3:1, and 0.1-0.25% of a polyacrylamide flocculant is added, and then the filtrate is obtained after pressure filtration after aging for 30-60 min.

[0067] In step S4, the secondary impurity removal filtrate is purified by using an ion exchange column, aiming to remove part of the aluminum and silicon impurities and the calcium impurities introduced in the previous step. The ion exchange column has the advantages of significant impurity removal effect, environmental friendliness and low cost.

[0068] In some embodiments, step S4 comprises: passing the secondary impurity removal filtrate through the ion exchange column at a flow rate of 1.5-2 BV / h. This flow rate range is advantageous for obtaining excellent impurity removal effect. The flow rate of the secondary impurity removal filtrate can typically but not limitatively be set at 1.5 BV / h, 1.6 BV / h, 1.7 BV / h, 1.8 BV / h, 1.9 BV / h, 2 BV / h.

[0069] In some embodiments, the ion exchange column is an ion exchange column packed with D201 macroporous resin.

[0070] In some embodiments, the ion exchange column has a column height to diameter ratio of 5:1.

[0071] In some embodiments, the residual Al in the obtained purified solution is <5 mg / L, and the residual Si is <5 mg / L.

[0072] In step S5, ammonium salt is added to the purified solution for vanadium precipitation.

[0073] In some embodiments, step S5 comprises: adjusting the pH of the purified solution to 8-9, adding ammonium salt, and crystallizing at 30-90℃ for 1-2 h to obtain ammonium metavanadate crystals. The pH can typically but not limitatively be adjusted to 8.0, 8.2, 8.4, 8.6, 8.8, 9.0. The reaction temperature can typically but not limitatively be set at 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, and the reaction time can typically but not limitatively be set at 1 h, 1.5 h, 2 h.

[0074] In some embodiments, the amount of ammonium salt added is 2-3.5 times the molar amount of vanadium in the basic vanadium leaching solution. The amount of ammonium salt added can typically but not limitatively be set at 2 times, 2.5 times, 3 times, 3.5 times the molar amount of vanadium in the basic vanadium leaching solution. + In some embodiments, the amount of ammonium salt added is 2-3.5 times the molar amount of vanadium in the basic vanadium leaching solution. The amount of ammonium salt added can typically but not limitatively be set at 2 times, 2.5 times, 3 times, 3.5 times the molar amount of vanadium in the basic vanadium leaching solution.

[0075] In some embodiments, the ammonium salt is ammonium carbonate or ammonium sulfate.

[0076] In step S6, the ammonium metavanadate crystals are calcined to obtain vanadium pentoxide.

[0077] In some embodiments, step S6 comprises: segmentally calcining the ammonium metavanadate crystals under an oxygen atmosphere, first increasing to 300°C at a rate of 5-10°C / min and maintaining for 0.5-1.5 h, and then increasing to 550°C at a rate of 2-8°C / min and maintaining for 1-3 h, to obtain high-purity vanadium pentoxide. The first-stage heating rate can be typically but not limitingly set to 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min, the first-stage holding time can be typically but not limitingly set to 0.5 h, 1 h, or 1.5 h, the second-stage heating rate can be typically but not limitingly set to 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, or 8°C / min, and the second-stage holding time can be typically but not limitingly set to 1 h, 1.5 h, 2 h, 2.5 h, or 3 h.

[0078] In step S7, a high-purity vanadium oxide electrode is prepared using the high-purity vanadium pentoxide. The high-purity vanadium pentoxide is a common positive electrode material for batteries (especially lithium-ion batteries and zinc-ion batteries). The high-purity vanadium pentoxide can be mixed with a conductive agent and a binder in a certain mass ratio to obtain a slurry, and the slurry can be compounded onto a current collector to obtain an electrode.

[0079] Specifically, in some embodiments, the high-purity vanadium oxide electrode is prepared by the following steps:

[0080] 1. Electrode slurry preparation

[0081] The binder PVDF (10% wt) is slowly added to N-methyl pyrrolidone (NMP), and magnetic stirring is performed until complete dissolution (50°C water bath acceleration). The conductive agent (one or both of carbon black and CNTs) and V2O5 are sequentially added, and planetary stirring (200-400 rpm, 1-3 hours) is followed by ultrasonic treatment (30 minutes) to eliminate agglomeration, wherein the solid content of the slurry is controlled to be 30-40%.

[0082] 2. Current collector treatment and coating

[0083] Current collector preparation: aluminum foil (lithium battery, thickness 15-20 pm) or carbon-coated aluminum foil (sodium battery) is ultrasonically cleaned with acetone / ethanol and dried.

[0084] Coating process: An automatic coating machine or a doctor blade is used, and the wet film thickness is controlled to be 150-200 pm (dry film about 50-70 pm). The coating speed is 10-20 mm / s, and the gap height is adjusted according to the viscosity of the slurry (usually 100-150 pm).

[0085] 3. Drying and compaction

[0086] Segmented drying: pre-volatilize the solvent at room temperature for 10-30 minutes, air-dry at 60-80℃ for 30-60 minutes, and then transfer to vacuum drying at 120-140℃ for 10-16 hours.

[0087] Rolling: use a roller compactor to compact, with a pressure of 5-10 MPa, so that the electrode density reaches 2.5-3.0 g / cm 3 (Thickness reduction of 20-30% after compaction).

[0088] The second aspect of the present application provides a high-purity vanadium oxide electrode prepared by the above method.

[0089] The present application is further described below in conjunction with specific examples, but in no way limits the present application. For the sake of brevity, if no special description is given, the methods used are all conventional methods.

[0090] Example 1

[0091] Raw material conditions: basic vanadium leaching solution pH=10.2, containing V 35.6g / L, Si 980mg / L, P 380mg / L, Al 320mg / L, Fe 45mg / L.

[0092] The preparation method of the high-purity vanadium oxide electrode comprises the following steps:

[0093] Step one: raw material pretreatment, the basic vanadium leaching solution is passed through an activated alumina adsorption column (Φ100×500mm, filled with 1-2mm particle size γ-Al2O3) at a flow rate of 3BV / h, the temperature is controlled at 50±2℃, and the Si content of the effluent is detected to be reduced to 602mg / L (removal rate 38.6%);

[0094] Step two: primary impurity removal, prepare a composite impurity removal agent, mix 50g of sodium lignosulfonate with 10g of chitosan, add 12mL of 0.1mol / L potassium persulfate solution, modify at 75℃ for 2 hours, add 20g of trisodium citrate complex, and prepare a 10% aqueous solution, add the composite impurity removal agent according to 1.2 times the V molar amount (i.e. 182g / m³ solution), under stirring at 300rpm, maintain pH=9.5±0.1, and react for 60 minutes, and after plate and frame pressure filtration, the Si content is 48mg / L, the P content is 52mg / L, and the Al content is 28mg / L;

[0095] Step three: secondary impurity removal, heat the filtrate to 85℃, add Ca(OH)2 suspension according to Ca / P=2.5:1, and synchronously add 0.2% of anionic polyacrylamide (molecular weight 8 million), after 30 minutes of heat stirring, pressure filtration, the filtrate composition is P 2.9mg / L, Ca 81mg / L;

[0096] Step four: deep purification, through a Φ150x750mm D201 resin column (loading height 600mm), control flow rate 1.8BV / h, effluent detection: Al 1.8mg / L, Si 2.3mg / L, Ca<0.5mg / L;

[0097] Step five: vanadium precipitation crystallization, adjust pH to 8.7 with dilute sulfuric acid, add (NH4)2SO4 to NH4 + V=3:1 (molar ratio), crystallize at 90℃ for 90 minutes to obtain ammonium metavanadate crystals (purity 99.2%);

[0098] Step six: calcination, first increase to 300℃ at 8℃ / min, keep for 1 hour, then increase to 550℃ at 5℃ / min, keep for 2 hours, obtain orange red V2O5 powder, detection results: purity: 99.96% (titration method), impurity content (ppm): Si 1.2, P 1.8, Al 1.5, Fe 0.8, specific surface area: 16.7m 2 / g (BET method), vanadium recovery rate: 98.9%;

[0099] Step seven: preparation of high-purity vanadium oxide electrode, mix V2O5 powder with conductive agent and adhesive agent according to a certain mass ratio to obtain slurry, and then composite the slurry onto the current collector to obtain the high-purity vanadium oxide electrode.

[0100] Example 2

[0101] Raw material conditions: basic vanadium leaching solution pH=9.8, containing V 32.4g / L, Si 1120mg / L, P 460mg / L, Al 280mg / L, Fe 35mg / L.

[0102] The preparation method of the high-purity vanadium oxide electrode comprises the following steps:

[0103] Step one: raw material pretreatment, pass the basic vanadium leaching solution through an activated alumina adsorption column (Φ100x500mm, packed with 1-2mm particle size γ-Al2O3) at a flow rate of 2BV / h, control temperature 50±2℃, and reduce Si content in the effluent, removal rate 42.1%;

[0104] Step two: primary impurity removal, prepare a composite impurity removal agent, mix 60g of sodium lignosulfonate with 10g of chitosan, add 12mL of 0.1mol / L potassium persulfate solution, modify at 60℃ for 2 hours, add 15g of trisodium citrate, and prepare a 10% aqueous solution, add the composite impurity removal agent at 1.1 times the V molar amount, maintain pH=9.7 under stirring at 350rpm, and react for 60 minutes, and then measure Si 50mg / L, P 51mg / L, and Al 30mg / L after plate and frame pressure filtration;

[0105] Step three: secondary impurity removal, the filtrate was heated to 95℃, Ca(OH)2 suspension was added according to Ca / P=2.8:1, and 0.15% anionic polyacrylamide (molecular weight 8 million) was added synchronously, after 40 minutes of insulation and stirring, pressure filtration was performed, and the filtrate composition was P 3.2 mg / L, Ca 85 mg / L;

[0106] Step four: deep purification, through a Φ150×750mm D201 resin column (loading height 600mm), the flow rate was controlled at 1.6BV / h, and the effluent detection was Al 1.9mg / L, Si 2.1mg / L, Ca<0.5mg / L;

[0107] Step five: vanadium precipitation and crystallization, the pH was adjusted to 9 by dilute sulfuric acid, (NH4)2CO3 was added to NH4 + / V=2.5:1 (molar ratio), and ammonium metavanadate crystals (purity 99.91%) were obtained after 60 minutes of crystallization at 90℃;

[0108] Step six: calcination, first increased to 300℃ at 6℃ / min and kept for 1 hour, then increased to 550℃ at 6℃ / min and kept for 2 hours in a muffle furnace, orange red V2O5 powder was obtained, and the detection results were: purity: 99.94% (titration method), impurity content (ppm): Si 1.2, P 1.6, Al 1.4, Fe 0.9, specific surface area: 16.7m 2 / g (BET method), vanadium recovery rate: 98.5%;

[0109] Step seven: preparation of high-purity vanadium oxide electrode, V2O5 powder was mixed with conductive agent and adhesive agent according to a certain mass ratio to obtain slurry, and the slurry was compounded on the current collector to obtain a high-purity vanadium oxide electrode.

[0110] Example 3

[0111] Raw material conditions: basic vanadium leaching solution pH=10.5, containing V 37.4g / L, Si 850mg / L, P 320mg / L, Al 320mg / L, Fe 42mg / L.

[0112] The preparation method of the high-purity vanadium oxide electrode comprises the following steps:

[0113] Step one: raw material pretreatment, the basic vanadium leaching solution was passed through an activated alumina adsorption column (Φ100×500mm, packed with 1-2mm particle size γ-Al2O3) at a flow rate of 3BV / h, the temperature was controlled at 50±2℃, and the effluent detection showed that the Si content was reduced, and the removal rate was 41.2%;

[0114] Step two: primary impurity removal, 70 g of lignin sodium sulfonate was mixed with 10 g of chitosan, 12 mL of 0.1 mol / L potassium persulfate solution was added, and the mixture was modified at 80°C for 2 hours. Then 20 g of trisodium citrate was added to prepare a 10% aqueous solution. The complex impurity removal agent was added at 1.1 times the V molar amount. Under stirring at 350 rpm, the pH was maintained at 9.5, and the reaction was carried out for 60 minutes. After plate and frame pressure filtration, the Si content was 45 mg / L, the P content was 56 mg / L, and the Al content was 33 mg / L;

[0115] Step three: secondary impurity removal, the filtrate was heated to 80°C, Ca(OH)2 suspension was added at Ca / P=2.4:1, and 0.2% anionic polyacrylamide (molecular weight 8 million) was added synchronously. After 40 minutes of stirring and maintaining the temperature, the filtrate was pressure filtered. The P content was 3 mg / L, and the Ca content was 88 mg / L.

[0116] Step four: deep purification, the filtrate was passed through a Φ150×750 mm D201 resin column (loading height 600 mm) at a flow rate of 1.6 BV / h. The effluent was detected to have Al content of 1.8 mg / L, Si content of 2 mg / L, and Ca content of less than 0.5 mg / L.

[0117] Step five: vanadium precipitation and crystallization, the pH was adjusted to 9 with dilute sulfuric acid, (NH4)2CO3 was added to NH4 + / V=2.8:1 (molar ratio), and the mixture was crystallized at 90°C for 60 minutes to obtain ammonium metavanadate crystals.

[0118] Step six: calcination, the temperature was first increased to 300°C at a rate of 7°C / min and maintained for 1 hour, and then increased to 550°C at a rate of 5°C / min and maintained for 1 hour in a muffle furnace. Orange-red V2O5 powder was obtained. The detection results were as follows: purity: 99.95% (titration method), impurity content (ppm): Si 1.21, P 1.5, Al 1.6, Fe 0.9, specific surface area: 15.8 m 2 / g (BET method), and vanadium recovery rate: 98.9%.

[0119] Step seven: preparation of high-purity vanadium oxide electrode, V2O5 powder was mixed with a conductive agent and a binder in a certain mass ratio to obtain a slurry. The slurry was compounded onto a current collector to obtain a high-purity vanadium oxide electrode.

[0120] The high-purity vanadium oxide electrode prepared by the above examples is used to assemble a battery and test its performance. Taking a button cell as an example, the following is assembled in an argon glove box (H2O / O2<0.1 ppm): positive electrode: the V2O5 electrode sheet prepared by the above examples; negative electrode: lithium sheet (counter electrode) or sodium sheet; separator: Celgard 2400; electrolyte: 1M LiPF6 dissolved in EC / DMC (volume ratio 1:1) or 1M NaPF6 dissolved in EC / DEC. The test results show that the lithium battery performance is as follows: the initial discharge capacity can reach 250-280 mAh / g at 0.2C (1C=294 mA / g), and the capacity retention rate is ≥80% after 100 cycles (the performance needs to be optimized by carbon compounding later).

[0121] In summary, the scheme of the present application can (1) simultaneously and efficiently remove silicon, phosphorus and aluminum in an alkaline system; (2) avoid equipment corrosion and ammonia emission caused by the use of strong acid and strong base; and (3) simplify the production process of existing high-purity V2O5. Specifically, compared with the prior art, the following beneficial effects can be achieved: 1. The impurity removal efficiency is significantly improved: the impurity content in the final product is Si≤2ppm, P≤2ppm and Al≤2ppm (ICP-MS detection); 2. Environmentally friendly: the pH is maintained at 8-10 throughout the process, ammonia volatilization is reduced by more than 85%, and total nitrogen in wastewater is <50mg / L; 3. Economic benefits are improved: compared with the traditional process, the vanadium recovery rate is increased by more than 98.5%, and the cost of the impurity removal agent is reduced; 4. Excellent product performance: the specific surface area of the obtained V2O5 is 15-18m 2 / g (nitrogen adsorption method), and the Na and K contents are both <2ppm, meeting the requirements of battery (especially lithium battery) positive materials. The electrode prepared from the high-purity vanadium pentoxide has excellent specific capacity, cycle stability and rate performance.

[0122] Finally, it should be noted that the above-described examples are part of the embodiments of the present application, but not all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

Claims

1. A method for preparing a high-purity vanadium oxide electrode, characterized in that, Includes the following steps: S1: The alkaline vanadium leaching solution was pretreated using an activated alumina adsorption column to obtain a pretreated solution; S2: Add a composite impurity removal agent with modified lignin sulfonate as the main agent to the pretreatment liquid for primary impurity removal. After solid-liquid separation, the primary impurity-removed filtrate is obtained. S3: Add calcium hydroxide suspension and flocculant to the primary impurity-removed filtrate for secondary impurity removal. After solid-liquid separation, the secondary impurity-removed filtrate is obtained. S4: The secondary impurity removal filtrate is purified using an ion exchange column to obtain a purified solution; S5: Add ammonium salt to the purified solution to precipitate vanadium and obtain ammonium metavanadate crystals; S6: Calcining the ammonium metavanadate crystals to obtain high-purity vanadium pentoxide; S7: High-purity vanadium oxide electrode is prepared using the aforementioned high-purity vanadium pentoxide. The main component of the composite impurity remover is aminopolysaccharide-modified lignin sulfonate, and the composite impurity remover also includes citrate. The composite impurity remover is prepared by the following method: After mixing lignin sulfonate and amino polysaccharide in a certain proportion, potassium persulfate solution was added and oxidized at 60-80℃ for 1-3 hours to obtain amino polysaccharide modified lignin sulfonate. The aminopolysaccharide-modified lignin sulfonate is compounded with citrate to obtain the composite impurity remover.

2. The method for preparing a high-purity vanadium oxide electrode according to claim 1, characterized in that, Includes one or more of the following: Step S1 includes: passing the alkaline vanadium leaching solution through an activated alumina adsorption column at a flow rate of 1-5 BV / h, with the temperature controlled at 40-60℃, to obtain the pretreated solution; Step S2 includes: adding the composite impurity remover with modified lignin sulfonate as the main agent to the pretreatment liquid, maintaining the pH at 9-10, reacting under stirring conditions for 30-90 minutes, and obtaining the first-stage impurity-removed filtrate after solid-liquid separation; Step S3 includes: heating the primary impurity-removed filtrate to 60-100℃, adding the calcium hydroxide suspension and the flocculant, aging for 30-60 minutes, and obtaining the secondary impurity-removed filtrate after solid-liquid separation; Step S4 includes: passing the secondary impurity removal filtrate through the ion exchange column at a flow rate of 1.5-2 BV / h to obtain the purified solution; Step S5 includes: adjusting the pH of the purification solution to 8-9, adding the ammonium salt, and crystallizing at 30-90°C for 1-2 hours to obtain the ammonium metavanadate crystals; Step S6 includes: calcining the ammonium metavanadate crystals in segments under an oxygen atmosphere, first raising the temperature to 300℃ at 5-10℃ / min and holding for 0.5-1.5h, then raising the temperature to 550℃ at 2-8℃ / min and holding for 1-3h, to obtain the high-purity vanadium pentoxide.

3. The method for preparing a high-purity vanadium oxide electrode according to claim 1, characterized in that, The amount of the composite impurity remover added is 1.1-1.3 times the molar amount of vanadium in the alkaline vanadium leaching solution.

4. The method for preparing a high-purity vanadium oxide electrode according to claim 1, characterized in that, In the composite impurity remover, the mass ratio of lignin sulfonate, citrate, and aminopolysaccharide is 5-8:2-1:

1.

5. The method for preparing a high-purity vanadium oxide electrode according to claim 1, characterized in that, The amount of calcium hydroxide suspension added is 2-3 times the amount of phosphorus in the alkaline vanadium leachate, based on the molar amount of calcium.

6. The method for preparing a high-purity vanadium oxide electrode according to claim 1, characterized in that, The flocculant is a polyacrylamide flocculant with a mass fraction of 0.1-0.25%.

7. The method for preparing a high-purity vanadium oxide electrode according to claim 1, characterized in that, The amount of ammonium salt added is based on NH4 + The molar amount is 2-3.5 times that of vanadium in the alkaline vanadium leaching solution.

8. A high-purity vanadium oxide electrode, characterized in that, It is prepared by any one of the preparation methods described in claims 1-7.

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