A high-energy-density low-cost iodine-based flow battery and a preparation method thereof

Abstract

The application discloses a high-energy-density low-cost iodine-based flow battery and a preparation method thereof, and the iodine-based flow battery comprises positive and negative electrolyte, positive and negative electrodes, a diaphragm, an electrolyte tank and a circulating pump; the active substance of the positive electrolyte is iodide; the additives are thiocyanate, ethanol, adsorbents, three-dimensional porous materials and screening filter materials; the cations of the thiocyanate and the iodide are the same; the screening materials are wrapped on the surface of the three-dimensional porous materials; the active substance of the negative electrolyte is any one of sulfide, zinc salt, lithium salt, magnesium salt, aluminum salt and anthraquinone-2,7-disulfonic acid disodium salt or 12-phosphotungstic acid; the diaphragm is an ion exchange membrane subjected to ionization treatment; and the positive and negative electrodes are graphite felt or carbon felt. The application adds additives to the positive electrolyte of the iodine-based flow battery, fixes the active substance in the positive electrolyte, and unlocks more iodine ion (I − ) capacity through the complexation of the thiocyanate and iodine.

Description

Technical Field

[0001] This invention belongs to the field of flow battery energy storage technology, and relates to a high-energy-density, low-cost iodine-based flow battery and its preparation method. Background Technology

[0002] The inherent non-renewable nature of traditional fossil fuels and their severe environmental pollution have led to a vigorous development of new energy sources, such as wind, solar, and tidal energy. However, these new energy sources require stable energy storage devices to address their discontinuous and unstable nature. Redox flow batteries, with their high safety, long lifespan, power and energy decoupling, fast response speed, and large energy storage capacity, have become one of the most promising and ideal candidates for large-scale energy storage technology.

[0003] However, most traditional flow battery systems suffer from drawbacks such as low energy density, high cost, strong corrosivity, and high volatility. These problems greatly hinder the large-scale development and commercialization of redox flow batteries. Therefore, it is essential to develop a new type of high-energy-density, low-cost flow battery system.

[0004] Iodine-based flow batteries have broad development prospects due to the high solubility and low cost of iodides as active materials. However, during charging, iodine ions cannot reach their maximum capacity release, and active materials permeate through the separator to the negative electrode, resulting in iodine ion capacity loss. The formation of elemental iodine also causes blockage of the electrolyte circulation channel, limiting the development of iodine-based flow batteries. Therefore, developing an additive to promote the complete release of iodine ion capacity, unclog the electrolyte circulation channel, prevent active material permeation, maximize its energy density, and improve the performance of iodine-based flow batteries is of great significance. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a high-energy-density, low-cost iodine-based flow battery. An additive is added to the positive electrode electrolyte of the iodine-based flow battery to immobilize the active material within the electrolyte. Through the complexation of thiocyanate with elemental iodine, more iodine ions (I₂O₃) are unlocked. - This capacity improvement solves the problem of insufficient capacity utilization in existing iodine-based flow batteries.

[0006] Another objective of this invention is to provide a method for preparing a high-energy-density, low-cost iodine-based flow battery.

[0007] The technical solution adopted in this invention is a high-energy-density, low-cost iodine-based flow battery, comprising positive and negative electrolytes, positive and negative electrodes, a separator, an electrolyte tank, and a circulation pump. The active material in the positive electrolyte is iodide, and the additives include thiocyanate, ethanol, an adsorbent, a three-dimensional porous material, and a sieving and filtering material. The thiocyanate and iodide have the same cation.- With SCN - The molar ratio is 1.0–6.0:3.0; the ethanol concentration is 0.1–50%; the adsorbent concentration is 0.1–10%; and the sieved material is coated on the surface of a three-dimensional porous material.

[0008] The active substance of the negative electrode electrolyte is any one of sulfide, zinc salt, lithium salt, magnesium salt, aluminum salt, and anthraquinone-2,7-disulfonic acid disodium salt or 12-phosphotungstic acid, with a molar concentration of 1 to 8.0 M.

[0009] The diaphragm is an ion exchange membrane that has undergone ionization treatment;

[0010] The positive and negative electrodes are graphite felt or carbon felt.

[0011] A method for preparing a high-energy-density, low-cost iodine-based flow battery, specifically comprising the following steps:

[0012] S1, prepare a strong base solution in a beaker using deionized water, with a molar concentration of 0.1–10 M;

[0013] S2, Preparation of the diaphragm: The ion exchange membrane is immersed in deionized water for cleaning;

[0014] S3, Immerse the cleaned ion exchange membrane in the alkaline solution prepared in step S1 for ionization treatment; the ionization temperature is 50-100℃ and the time is 1-3h.

[0015] S4. Wash the membrane repeatedly with deionized water until the solution pH = 6-7, and then soak it in deionized water for use as an ion exchange membrane.

[0016] S5, Preparation of positive electrode electrolyte: Prepare an iodide solution using deionized water, and add thiocyanate as an additive. - The molar concentration is 1.0 M to 6.0 M, SCN - The molar concentration is 3.0 M; the iodide is KI, NaI, LiI or ZnI2, and the thiocyanate is NaSCN, KSCN, LiSCN or Zn(SCN)2; the adsorbent is starch, cyclodextrin, alginate, chitosan, metal-organic framework materials, covalent-organic framework materials or zeolite imidazole ester framework structure materials; the three-dimensional porous material is carbon felt, graphite felt, nickel mesh, activated carbon, zeolite or volcanic rock; the sieving and filtering material is PP fiber, polyester fiber, degreased cotton fiber or acrylic fiber;

[0017] S6, Preparation of negative electrode electrolyte: The negative electrode active material is prepared with deionized water, and the ion concentrations on both the positive and negative electrodes are the same.

[0018] S7 uses graphite felt or carbon felt as the positive and negative electrodes of the battery.

[0019] S8. Assemble the membrane, positive electrolyte, negative electrolyte, and positive and negative electrodes prepared in steps S4, S5, S6, and S7 into an iodine-based flow battery.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention adds additives to the positive electrode electrolyte of an iodine-based flow battery to fix the active material in the positive electrode electrolyte, reducing the permeation of the active material into the negative electrode electrolyte through the separator; through the complexation of thiocyanate and iodine, the capacity of iodine ions is unlocked, increasing the energy density of the iodine-based flow battery, solving the problem of low usable capacity of iodine ions, and increasing the battery energy density by one-third. It can effectively release the full capacity of iodine ions, significantly improving the actual capacity and energy density of the iodine-based redox flow battery, improving iodine utilization, reducing the cost of the iodine-based flow battery electrolyte, and improving battery cycle stability, ensuring the efficient and stable operation of the iodine-based flow battery with high iodine ion utilization.

[0022] 2. In this invention, thiocyanate and ethanol promote the dissolution of iodine and coat the sieve filter material on the surface of the three-dimensional porous material. When placed in the positive electrode electrolysis tank, it can not only adsorb active substances and reduce the permeation of positive electrode active substances, but also prevent large insoluble substances from rushing into the battery, solve the problem of blockage of the positive electrode electrolyte flow channel, reduce the corrosion of battery materials by iodine, improve the recyclability of battery materials, and reduce material costs.

[0023] 3. The high iodine ion utilization positive electrode system of this invention can be combined with various negative electrode active materials to form different flow battery systems, including the use of low-cost and highly soluble materials such as sulfides and zinc compounds as negative electrode active materials, further reducing electrolyte costs. Low-cost, high-performance separators such as SPEEK, SPES, and PBI can replace Nafion membranes in the assembly of iodine-based flow batteries, significantly reducing material costs.

[0024] 4. The raw materials used in this invention are readily available, low in cost, simple in preparation process, easy to operate, and inexpensive in equipment, making it suitable for large-scale industrial development. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1This is a comparison graph of the capacity and voltage of Example 1 and the sulfur-iodine flow battery without additives.

[0027] Figure 2 This is a comparison graph of the capacity and voltage of Example 2 and the sulfur-iodine flow battery without additives.

[0028] Figure 3 This is a comparison graph of the capacity and voltage of Example 3 and the sulfur-iodine flow battery without additives.

[0029] Figure 4 The sulfur-iodine flow battery of Example 1 operates at 20 mA cm⁻¹ -2 Efficiency and capacity retention at current density.

[0030] Figure 5 The sulfur-iodine flow battery of Example 2 operates at 20 mA cm⁻¹ -2 Efficiency and capacity retention at current density.

[0031] Figure 6 The sulfur-iodine flow battery of Example 3 was tested at 20 mA cm⁻¹. -2 Efficiency and capacity retention at current density.

[0032] Figure 7 The sulfur-iodine flow battery of Example 1 operates at 10 mA cm⁻¹ -2 ~50mA cm -2 Efficiency graph at current density.

[0033] Figure 8 This is a comparison graph of the capacity and voltage of Example 4 and the zinc-iodine flow battery without additives.

[0034] Figure 9 This is a comparison graph of the capacity and voltage of Example 5 and the zinc-iodine flow battery without additives.

[0035] Figure 10 This is a comparison graph of the capacity and voltage of Example 6 and the zinc-iodine flow battery without additives.

[0036] Figure 11 The zinc-iodine flow battery of Example 4 was tested at 20 mA cm⁻¹. -2 Efficiency and capacity retention at current density.

[0037] Figure 12 The zinc-iodine flow battery of Example 5 was tested at 20 mA cm⁻¹. -2 Efficiency and capacity retention at current density.

[0038] Figure 13 This is a comparison graph of the capacity and voltage of Example 7 and the sulfur-iodine flow battery without additives.

[0039] Figure 14 This is a comparison graph of the capacity and voltage of Example 8 and the sulfur-iodine flow battery without additives.

[0040] Figure 15 This is a comparison graph of the capacity and voltage of Example 9 and the zinc-iodine flow battery without additives.

[0041] Figure 16 This is a comparison graph of the capacity and voltage of Example 10 and an iodine-based flow battery without additives.

[0042] Figure 17 This is a comparison graph of the capacity and voltage of Example 11 and an iodine-based flow battery without additives.

[0043] Figure 18 This is a comparison graph of the capacity and voltage of Example 12 and an iodine-based flow battery without additives.

[0044] Figure 19 This is a comparison graph of the capacity and voltage of Example 13 and an iodine-based flow battery without additives.

[0045] Figure 20 This is a comparison graph of the capacity and voltage of Example 14 and an iodine-based flow battery without additives.

[0046] Figure 21 This is a comparison graph of the capacity and voltage of Example 15 and an iodine-based flow battery without additives.

[0047] Figure 22 This is a comparison graph of the capacity and voltage of Example 16 and an iodine-based flow battery without additives.

[0048] Figure 23 This is a comparison graph of the capacity and voltage of Example 17 and the sulfur-iodine flow battery without additives.

[0049] Figure 24 This is a comparison graph of the capacity and voltage of Example 18 and the sulfur-iodine flow battery without additives.

[0050] Figure 25 This is a comparison graph of the capacity and voltage of Example 19 and the sulfur-iodine flow battery without additives.

[0051] Figure 26 This is a comparison graph of the capacity and voltage of Example 20 and the sulfur-iodine flow battery without additives.

[0052] Figure 27 This is a comparison graph of the capacity and voltage of Example 21 and the sulfur-iodine flow battery without additives.

[0053] Figure 28 This is a comparison graph of the capacity and voltage of Example 22 and the sulfur-iodine flow battery without additives.

[0054] Figure 29 This is a comparison graph of the capacity and voltage of the iodine-based flow battery in Comparative Example 1.

[0055] Figure 30 The graph shows the capacity retention of the iodine-based flow battery in Comparative Example 1.

[0056] Figure 31 This is a polarization test diagram of the zinc-iodine flow battery assembled in Example 4. Detailed Implementation

[0057] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0058] Traditional iodine-based flow batteries suffer from capacity loss due to the loss of one-third of iodine ions during charging, limiting their maximum energy density. This invention addresses this issue by adding thiocyanate to the positive electrode electrolyte of traditional iodine-based flow batteries. Through the complexation of thiocyanate with elemental iodine, the iodine ion capacity is unlocked, increasing the energy density of the iodine-based flow battery and solving the problem of low usable iodine ion capacity. This results in a one-third increase in battery energy density. The invention's battery testing design incorporates dual-condition control of voltage and theoretical capacity. This maximizes the release of iodine ion capacity while preventing side reactions, ensuring the reversibility of the redox reaction, and guaranteeing stable charge-discharge cycle testing. In contrast, existing technologies only design voltage control for battery testing, which can easily lead to incomplete oxidation of iodine ions during charging before reaching the cutoff voltage, resulting in ineffective utilization of iodine ions and significant capacity loss.

[0059] Example

[0060] A method for preparing a high-energy-density iodine-based flow battery includes the following steps:

[0061] S1. Prepare a strong base solution in a beaker using deionized water; the strong base solution is an aqueous solution of KOH, NaOH, or LiOH, with a molar concentration of 0.1–10 M.

[0062] In this example, the strong alkaline solution used to treat the separator is specifically KOH. The reasons are as follows: 1. The positive electrode active material used in the separator test of this example is KI, the additive is KSCN, the negative electrode active material in the sulfur-iodine system is K2S, and the supporting electrolyte is KBr. The supporting electrolyte in the zinc-iodine system is also KBr. During the battery charging and discharging process, K... +It passes through the separator and is transferred between the positive and negative electrodes to complete the battery's redox reaction. Therefore, the separator, located between the positive and negative electrodes, not only needs to block the shuttle between the active materials of the positive and negative electrodes, but also needs to conduct K. + This ensures the smooth progress of the battery charging and discharging reaction. 2. The Nafion membrane is treated with KOH to remove the H+ from the sulfonic acid groups (-SO3H) in the membrane. + K in KOH + Substitution forms -SO3K groups, yielding a Nafion-K membrane, in which K... + The channel is opened, enabling the effective transmission of K. + This ensures the smooth progress of the battery's charging and discharging reactions. In some embodiments, the positive electrode active material of the iodine-based battery is sodium iodide (NaI), and the supporting electrolyte can be sodium thiocyanate (NaSCN). The thiocyanate ion (SCN) in NaSCN... - This can achieve the release of iodide ions (I) from NaI. - Regarding capacity effects, in the sulfur-iodine system, the negative electrode active material can be Na₂S, and the supporting electrolyte can be NaBr or NaCl. Similarly, in the zinc-iodine system, the supporting electrolyte can also be NaBr or NaCl. + In order to complete the redox reaction of the battery by transferring energy between the positive and negative electrodes, the separator needs to be treated with an alkaline solution (NaOH). The Na in the separator... + The channel is opened, resulting in a Nafion-Na membrane, which can effectively transfer Na. + This ensures the smooth progress of the battery's charging and discharging reactions. If LiI is used as the positive electrode active material, LiSCN can be used as the positive electrode supporting electrolyte, and LiBr or LiCl can be used as the negative electrode supporting electrolyte. The separator can be treated with LiOH solution, and then... + The redox reaction is carried out between the positive and negative electrodes; if ZnI2 is used as the active material of the positive electrode, Zn(SCN)2 can be used as the supporting electrolyte, and ZnBr2 or ZnCl2 can be used as the supporting electrolyte of the negative electrode. The separator can be treated with ZnCl2 solution. 2+ The transfer of salt ions between the positive and negative electrodes completes the redox reaction of the battery. Therefore, the separator can be treated with strong alkaline solutions such as KOH, NaOH, or LiOH aqueous solutions for use in iodine-based flow batteries to transfer salt ions (K+, NaOH, LiOH, etc.). + Na + Li + Zn 2+ (etc.) to complete the battery oxidation-reduction reaction.

[0063] In this embodiment, the strong alkaline solution (KOH) used to treat the separator had a molar concentration of 1.0 M. Under the same conditions, the higher the alkaline concentration, the longer the treatment time, and the higher the temperature, the higher the degree of ionization of the separator, until saturation. However, in an alkaline environment, the separator is easily degraded, and its mechanical properties decrease. Under the same conditions, the higher the alkaline concentration, the longer the treatment time, and the higher the temperature, the greater the impact on the mechanical properties of the separator, and the lower the electrochemical stability of the battery. Therefore, in this embodiment, the best effect was achieved when the Nafion separator was ionized in a KOH solution at a constant temperature of 80°C for 1.5 h with a KOH concentration of 1.0 M. This resulted in a separator with a high degree of ionization while maintaining its mechanical properties, enabling the battery to operate efficiently and stably.

[0064] S2, preparation of the diaphragm: the ion exchange membrane is soaked in deionized water for cleaning; the cation exchange membrane is a Nafion membrane, SPEEK membrane, SPES membrane or PBI membrane.

[0065] In the embodiments, the separator plays a role in preventing cross-contamination of positive and negative electrode active materials and transferring salt ions to complete the battery circuit. However, each type of separator has its own advantages and disadvantages. For example, Nafion separators have strong mechanical properties and high ion conductivity, but their high ion permeability and high manufacturing cost, coupled with DuPont's technological monopoly, create a "bottleneck" problem that limits the further application of Nafion separators. SPEEK and SPES membranes have the characteristics of low cost and controllable proton conductivity, but high-sulfonation SPEEK membranes have lower mechanical properties, making it difficult to achieve high proton conductivity, high ion selectivity, and high mechanical properties simultaneously. PBI membranes have good thermal stability and mechanical properties, and the polymer contains both proton donors and acceptors. However, their low conductivity and difficulty in film formation greatly limit the application of PBI membranes.

[0066] S3. Immerse the ion exchange membrane obtained in S2 in the alkaline solution of S1 for ionization treatment; the ionization temperature is 50-100℃, and the time is 1-3 hours. The purpose is to open as many salt ion channels in the membrane as possible (e.g., to open all H+ ions in the -SO3H+ ion channels of the Nafion membrane). + Replace with K + This allows salt ions in the positive and negative electrode solutions to quickly pass through the separator during charge and discharge testing, promoting the redox reaction at the positive and negative electrodes and improving battery performance. If only the normal temperature conditions during battery cycling are relied upon, salt ion channels are difficult to form, affecting the salt ion conduction rate and consequently impacting battery performance.

[0067] S4. The membrane obtained in S3 is repeatedly washed with deionized water until the solution pH is 6-7, and then soaked in deionized water for use as an ion exchange membrane.

[0068] S5, Preparation of positive or negative electrode electrolyte: An iodide solution is prepared using deionized water, and KSCN is added as an additive to serve as the positive electrode electrolyte. The active material in the positive electrode electrolyte is iodide, which can be KI, NaI, LiI, or ZnI2, with a molar concentration of 0.1–12.0 M. Additives include thiocyanate, ethanol, adsorbent, three-dimensional porous materials, and sieve filtration materials. The thiocyanate can be NaSCN, KSCN, LiSCN, or Zn(SCN)2, with a molar concentration of... The concentration of the ethanol is 0.1–6.0 M; the concentration of the adsorbent is 0.1–50%; the adsorbent is starch, cyclodextrin, alginate, chitosan, metal-organic framework material, covalent-organic framework material or zeolite imidazole ester framework material, with a concentration of 0.1–10%; the three-dimensional porous material is carbon felt, graphite felt, nickel mesh, activated carbon, zeolite or volcanic rock; the sieving filter material is cloth-like PP fiber, polyester fiber, degreased cotton fiber, degreased fiber or acrylic fiber; the sieving material is wrapped on the surface of the three-dimensional porous material.

[0069] Metal-organic framework materials, such as UIO-66 and MIL-53. Zeolite imidazole ester framework materials are special metal-organic framework materials with imidazole or its derivatives as ligands, such as ZIF-8 and ZIF-90. Covalent organic framework materials, such as COF-316 and COF-318.

[0070] SCN - The molar concentration is 3.0 M, I - Molar concentrations from 1.0 M to 6.0 M can all achieve the release of additional IgA. - The effect of capacity. This is because of SCN. - Release I - The theoretical capacity ratio is 1:2 (1.0M SCN). - It can promote 2.0MI - (Releasing an additional third of capacity), the higher the thiocyanate concentration, the better the effect on iodine ion capacity release. However, the increase in thiocyanate also increases the battery's internal resistance, affecting the battery's electrochemical performance. Therefore, when I... - At molar concentrations of 1.0 M to 6.0 M, 3.0 MSCN - Able to reach I - While effectively releasing capacity, reduce SCN - The impact on the electrochemical performance of the battery.

[0071] The optimal pairings of iodides and thiocyanates are KI with KSCN, NaI with NaSCN, LiI with LiSCN, and ZnI₂ with Zn(SCN)₂. This is because both substances can provide the same salt ion (K₂). + Na + Li+ Zn 2+ This can increase the salt ion concentration, promote the salt ion transfer rate, and ensure the completion of the redox reaction at the positive and negative electrodes of the battery.

[0072] S6, Preparation of negative or positive electrode electrolyte: A negative electrode active material and its supporting electrolyte aqueous solution are prepared using deionized water as the negative electrode electrolyte; the active material of the negative electrode electrolyte is a sulfide, zinc salt, lithium salt, magnesium salt, and some organic matter; the sulfide is K2S, Na2S, or Li2S, with a molar concentration of 1–8.0 M; the zinc salt is ZnI2, ZnBr2, or ZnCl2; the lithium salt is LiI, LiBr, or LiCl; the magnesium salt is MgI2, MgBr2, or MgCl2; the sodium salt is Na... I, NaBr, NaCl; aluminum salts are AlI3, AlCl3, AlBr3; some organic compounds include disodium anthraquinone-2,7-disulfonic acid and 12-phosphotungstic acid; supporting electrolytes are KI, KBr, KCl, NaI, NaBr, NaCl, NH4I, NH4Br, NH4Cl, LiI, LiBr, or LiCl; the positive electrode electrolyte has wide adaptability and can be matched with various negative electrode active materials to assemble redox flow batteries of different systems.

[0073] When the active material and supporting electrolyte of the negative electrode are the same as the cations of the positive electrode active material, the electrolyte has fewer ion types, resulting in smaller concentration polarization and better battery performance. When the negative electrode active material does not contain the same cations as the positive electrode active material or supporting electrolyte, adding a supporting electrolyte with the same cations can reduce the number of ions in the electrolyte while ensuring the internal circuitry of the battery, thus maintaining battery performance. When the positive electrode active material is KI, K₂S can be chosen as the negative electrode active material, and potassium salts such as KCl and KBr can be used as the supporting electrolyte. When zinc salts, lithium salts, magnesium salts, or some organic compounds are used as the negative electrode active material, potassium salts such as KCl and KBr can also be used as the supporting electrolyte. When the positive electrode active material is NaI, LiI, or ZnI₂, sodium salts, lithium salts, and zinc salts can be chosen as the supporting electrolyte.

[0074] Examples of iodine-based redox flow batteries were assembled using sulfides, zinc salts, lithium salts, magnesium salts, aluminum salts, and disodium anthraquinone-2,7-disulfonic acid and 12-phosphotungstic acid as negative electrode active materials. This improved the thiocyanate unlocking I... - The universality of capacity provides various possible development directions for iodine-based flow batteries.

[0075] The negative electrode active material can be sulfides, zinc salts, lithium salts, or some organic compounds, matched with the iodine positive electrode to assemble various iodine-based redox flow batteries, such as sulfur-iodine batteries, zinc-iodine batteries, lithium-iodine batteries, magnesium-iodine batteries, aluminum-iodine batteries, and organic / iodine batteries. The negative electrode needs to be selected from active materials that provide the same salt ions as the positive electrode active material and the supporting electrolyte. For example, if the positive electrode provides K+ ions... + Therefore, the negative electrode needs to be selected to provide K+ salt ions. + The active substance (K2S).

[0076] The conditions that the molar concentration of the negative electrode active material must meet are: 1. When electrons are transferred during the redox reaction at the positive electrode, the negative electrode active material must provide the same number of transferred electrons during the redox reaction. 2. The ion concentrations on both sides of the positive and negative electrodes should be kept as equal as possible to reduce water migration between the electrodes. When both conditions are met, the molar concentration of the negative electrode active material is optimal, and the effect is best.

[0077] The supporting electrolyte is determined based on the ions provided by the active materials at the positive and negative electrodes, serving to provide salt ions and balance the ion concentrations at both electrodes. When the salt ions provided by the active material are K+... + At the same time, the supporting electrolyte also uses salt ions that can provide K+. + Supporting electrolytes, such as KSCN, KBr, and KCl, are used. The molar concentration of the supporting electrolyte is related to the ion concentration provided by the active materials of the positive and negative electrodes. The molar concentration that minimizes the ion concentration difference between the positive and negative electrode electrolytes and the water migration between the positive and negative electrodes is the most effective supporting electrolyte molar concentration.

[0078] The optimal pairing of the negative electrode active material and the supporting electrolyte is two substances that can reduce the types of ions in the electrolyte, provide the same type of salt ions, and are relatively inexpensive. For example, ZnBr2 and KBr or NaBr.

[0079] The negative electrode uses sulfides ZnS, LiI, LiBr, and LiCl, MgI2, MgBr2, MgCl2, AlI3, AlCl3, and AlBr3 as active materials, which can provide active ions S2 that match the iodine ions of the positive electrode. 2- Li + Mg 2+ Al 3+ Therefore, the above-mentioned substances can be used as negative electrode active materials to match and assemble iodine-based redox flow batteries with iodine positive electrodes.

[0080] S7 uses graphite felt or carbon felt as the positive and negative electrode materials of the battery. The thickness of the graphite felt or carbon felt is 3 to 8 mm. The thicker the graphite felt or carbon felt, the more active sites it provides. However, excessive thickness will increase the battery resistance and affect the battery's electrochemical performance. Therefore, it is necessary to select graphite felt or carbon felt with appropriate thickness.

[0081] S8. Assemble the separator, positive electrolyte, negative electrolyte, and positive and negative electrodes prepared in S4, S5, S6, and S7 into an iodine-based flow battery, and test it using a battery testing system.

[0082] Example 1,

[0083] A method for preparing a high-energy-density iodine-based flow battery includes the following steps:

[0084] 1. Preparation of membrane material (this embodiment uses ionized Nafion 212):

[0085] (1) Immerse a Nafion membrane with a length of 7.5cm and a width of 5.0cm in deionized water and wash it repeatedly;

[0086] (2) The cleaned Nafion membrane was placed in a 1.0 M potassium hydroxide aqueous solution at a constant temperature of 80 °C for 2 h for ionization.

[0087] (3) Rinse the ionized Nafion membrane repeatedly with deionized water until it is neutral, then soak it in deionized water for later use.

[0088] 2. Preparation of electrode materials: Carbon felt with a length of 4.5 cm, a width of 3.0 cm, and a thickness of 5.0 mm was used as the positive and negative electrode materials of the battery.

[0089] 3. Preparation of electrolyte:

[0090] Preparation of positive electrode electrolyte: Dissolve KI and KSCN in water to prepare a solution with a KI molar concentration of 1.0 M, a KSCN molar concentration of 3.0 M, an ethanol concentration of 10%, and a starch concentration of 1%. After complete dissolution, take a certain amount of the solution and place it in the positive electrode storage tank. Add carbon felt wrapped with degreased cloth fibers to the positive electrode storage tank to serve as the positive electrode electrolyte of the battery.

[0091] Preparation of negative electrode electrolyte: K2S is dissolved in water to a molar concentration of 4.0M. After complete dissolution, a certain amount of the solution is placed in the negative electrode storage tank as the negative electrode electrolyte of the battery.

[0092] In this embodiment, a KI, KSCN, ethanol, and starch aqueous solution with degreased fiber-wrapped carbon felt was used as the positive electrode electrolyte, and a K2S aqueous solution was used as the negative electrode electrolyte. Carbon felt was used as both the positive and negative electrode materials of the flow battery, and an ionized Nafion 212 membrane was used as the separator. The key materials were assembled into a sulfur-iodine flow battery, and the battery was tested using a Newway testing system. The charge / discharge current density was 20 mA cm⁻¹. -2 .

[0093] The capacity and voltage of the iodine-based flow battery prepared in Example 1 are as follows: Figure 1 As shown, comparing the capacity-voltage curves of the sulfur-iodine flow battery with and without additives, it can be found that one-third of the capacity of the traditional sulfur-iodine flow battery (1.0 MKI, without additives) is lost. However, the capacity-voltage curve after adding the additive KSCN shows that the usable capacity is increased by one-third, reaching the theoretical capacity of 268 mAh. The results of the examples show that the present invention, when used in the positive electrode electrolyte containing 1.0 M iodine ion reactive material in the sulfur-iodine flow battery, can increase the actual capacity by one-third compared to the traditional sulfur-iodine flow battery.

[0094] Efficiency performance of the iodine-based flow battery prepared in Example 1 Figure 4 As shown, the sulfur-iodine flow battery with added additives can maintain a coulombic efficiency of 99% while releasing the full capacity of iodine ions, and can stably cycle for more than 90 cycles with a capacity retention rate of over 99%. The results of the examples demonstrate that the present invention, when used in a positive electrode electrolyte containing 1.0 M iodine ion reactive material, can achieve stable cycling in a sulfur-iodine flow battery.

[0095] Figure 1 , 4 The test program is a loop test program. Figure 1 This is to highlight the effectiveness of 3.0 MKSCN in a sulfur-iodine flow cell compared to 1.0 MI. - The release of capacity, and Figure 4 This is to highlight that the additive of the present invention not only promotes 1.0 MI, but also that 3.0 MKSCN can promote 1.0 MI. - The release of capacity, along with the addition of ethanol, starch, defatted fiber, and carbon felt in the additives, ensures that the active substance content is 1.0 MI. - Stable cycling of sulfur-iodine flow batteries.

[0096] The iodine-based flow battery prepared in Example 1 was subjected to long-cycle testing using a Newway testing system. The test program was a rate test program, such as... Figure 7 As shown. The charging and discharging current densities are 10 mA cm⁻¹, respectively. -2 20mA cm -2 30mA cm -2 40mA cm -2 50mA cm -2 10mA cm -2 The battery rate performance was tested using the Xinwei testing platform. The current density of the test battery was controlled by a program designed using Xinwei testing software. The battery reaction area was known, and the test current of the equipment could be controlled accordingly, which is known in the field.

[0097] Depend on Figure 7 It can be seen that the sulfur-iodine flow battery with added additives operates at 10 mA cm⁻¹. -2~50mA cm -2 The battery exhibits stable cycling within a wide current density range, achieving a coulombic efficiency exceeding 99%. Furthermore, even after cycling at high current densities and then returning to low current densities, it maintains high battery efficiency. Example results demonstrate that this invention, when used in a sulfur-iodine flow battery with a positive electrode electrolyte containing iodine-ion reactive materials, effectively releases the full capacity of iodine ions while maintaining high efficiency at 10 mA cm⁻¹. -2 ~50mA cm -2 It can cycle stably within the current density range and achieve good battery efficiency. Figure 7 This is to highlight the demonstration that 3.0M KSCN releases 1.0M. - Electrochemical performance of a sulfur-iodine flow battery at different current densities.

[0098] Example 2,

[0099] The difference from Example 1 is that the molar concentration of KI in the positive electrode electrolyte is 3.0 M and the molar concentration of K2S in the negative electrode electrolyte is 6.0 M.

[0100] In this embodiment, a KI, KSCN, ethanol, and starch aqueous solution with degreased fiber-wrapped carbon felt was used as the positive electrode electrolyte, and a K2S aqueous solution was used as the negative electrode electrolyte. Carbon felt was used as both the positive and negative electrode materials of the flow battery, and an ionized Nafion 212 membrane was used as the separator. The key materials were assembled into a sulfur-iodine flow battery, and the battery was tested using a Newway testing system. The charge / discharge current density was 20 mA cm⁻¹. -2 .

[0101] The capacity and voltage of the iodine-based flow battery prepared in Example 2 are as follows: Figure 2 As shown, comparing the capacity-voltage graphs of a sulfur-iodine flow battery with and without additives, it can be seen that one-third of the capacity of the traditional sulfur-iodine flow battery (KI 3.0M, without additives) is lost. However, the capacity-voltage curve after adding the additive KSCN shows that the usable capacity is increased by one-third, reaching the theoretical capacity of 804mAh. The results of the examples demonstrate that the present invention, used in a positive electrode electrolyte containing 3.0M iodine ion reactive material in a sulfur-iodine flow battery, can increase the actual capacity by one-third compared to the traditional sulfur-iodine flow battery.

[0102] Efficiency performance of the iodine-based flow battery prepared in Example 2 Figure 5 As shown, the sulfur-iodine flow battery with added additives can maintain a 99% coulombic efficiency while releasing the full capacity of iodine ions, and can stably cycle for more than 60 cycles with a capacity retention rate of over 99%. The results of the examples demonstrate that the present invention, when used in a positive electrode electrolyte containing 3.0M iodine ion reactive material, can achieve stable cycling in a sulfur-iodine flow battery. Figure 2This is to highlight the effectiveness of 3.0 MKSCN in sulfur-iodine flow batteries compared to 3.0 MI. - The release of capacity, and Figure 5 This is to highlight that the additive of the present invention not only promotes 3.0 MI, but also... - The release of capacity, and the addition of ethanol, starch, defatted fiber, and carbon felt in the additives, ensures that the active substance content is 3.0 MI. - Stable cycling of sulfur-iodine flow batteries.

[0103] Example 3,

[0104] The difference from Example 1 is that the molar concentration of KI in the positive electrode electrolyte is 6.0 M and the molar concentration of K2S in the negative electrode electrolyte is 8.0 M.

[0105] The capacity and voltage of the iodine-based flow battery prepared in Example 3 are as follows: Figure 3 As shown, comparing the capacity-voltage graphs of a sulfur-iodine flow battery with and without additives, it can be found that one-third of the capacity of the traditional sulfur-iodine flow battery (KI 6.0M, without additives) is lost. However, the capacity-voltage curve after adding the additive KSCN shows that the usable capacity is increased by one-third, reaching the theoretical capacity of 1608mAh. The results of the examples demonstrate that the present invention, used in a positive electrode electrolyte containing 6.0M iodine ion reactive material in a sulfur-iodine flow battery, can increase the actual capacity by one-third compared to the traditional sulfur-iodine flow battery.

[0106] Efficiency performance of the iodine-based flow battery prepared in Example 3 Figure 6 As shown, the sulfur-iodine flow battery with added additives can maintain a 99% coulombic efficiency while releasing the full capacity of iodine ions, and can cycle stably for more than 18 cycles with a capacity retention rate of over 99%. The results of the examples demonstrate that the present invention, when used in a positive electrode electrolyte containing 6.0M iodine ion reactive material, can achieve stable cycling in a sulfur-iodine flow battery. Figure 3 This is to highlight the effectiveness of 3.0 MKSCN in a sulfur-iodine flow cell compared to 6.0 MI. - The release of capacity, and Figure 6 This is to highlight that the additive of the present invention not only promotes 6.0 MI, but also that 3.0 MKSCN can promote MI. - The release of capacity, and the addition of ethanol, starch, defatted fiber, and carbon felt in the additives, ensures that the active substance content is 6.0 MI. - Stable cycling of sulfur-iodine flow batteries.

[0107] Example 4,

[0108] A method for preparing a high-energy-density iodine-based flow battery differs from Example 1 in that: Negative electrode electrolyte preparation: ZnBr2, NH4Br, and KBr are dissolved in water, and the three solutions are mixed. The molar concentrations of ZnBr2, NH4Br, and KBr are 1.0 M, 3.0 M, and 2.0 M, respectively. After complete dissolution, a certain amount of this solution is placed in a negative electrode storage tank as the negative electrode electrolyte of the battery; wherein KBr is the negative electrode supporting electrolyte.

[0109] In this embodiment, ZnBr2 is the negative electrode active material, and NH4Br and KBr are the negative electrode supporting electrolytes of the zinc-iodine flow battery, providing Zn 2+ , with I in the positive electrode - They pair to form redox couples, completing the redox reaction in the flow battery. NH4Br promotes the dissolution of zinc dendrites, mitigating their formation at the negative electrode. Zinc dendrites easily puncture the separator, causing a short circuit. KBr provides K... + K + It shuttles between the positive and negative solutions to complete the battery circuit, and is equivalent to KBr in the positive electrode solution, reducing the osmotic pressure between the positive and negative electrodes and reducing water migration between them.

[0110] The capacity and voltage of the iodine-based flow battery prepared in Example 4 are as follows: Figure 8 As shown, comparing the capacity-voltage curves of zinc-iodine flow batteries with and without additives, it can be found that one-third of the capacity of the traditional zinc-iodine flow battery (KI 1.0M, without additives) is lost. However, the capacity-voltage curve after adding the additive KSCN shows that the usable capacity is increased by one-third, reaching the theoretical capacity of 268mAh. The results of the examples demonstrate that when the present invention is used in a positive electrode electrolyte containing 1.0M iodide ion reactive material in a zinc-iodine flow battery, the actual capacity can be increased by one-third compared to the traditional zinc-iodine flow battery.

[0111] The efficiency performance of the iodine-based flow battery prepared in Example 4 is as follows: Figure 11 As shown, the zinc-iodine flow battery with added additives can maintain a 99% coulombic efficiency while releasing the full capacity of iodine ions, and can stably cycle for more than 50 cycles with a capacity retention rate of over 99%. The results of the examples demonstrate that the present invention, when used in a positive electrode electrolyte containing 1.0 M iodine ion reactive material, can achieve stable cycling in a zinc-iodine flow battery.

[0112] Figure 8 This is to highlight the demonstration effect of 3.0 M KSCN for 1.0 M KSCN in zinc-iodine flow cells. - The release of capacity, and Figure 11 This is to highlight that the additive of the present invention not only promotes 1.0 M KSCN, but also that 3.0 M KSCN can promote 1.0 M KSCN. -The release of capacity, and the addition of ethanol, starch, defatted fiber, and carbon felt in the additives, ensures that the active substance content is 1.0 MI. - Stable cycling of zinc-iodine flow batteries.

[0113] Example 5,

[0114] The difference from Example 4 is that the KI molar concentration in the positive electrode electrolyte is 3.0 M.

[0115] The capacity and voltage of the iodine-based flow battery prepared in Example 5 are as follows: Figure 9 As shown, comparing the capacity-voltage curves of zinc-iodine flow batteries with and without additives, it can be found that one-third of the capacity of the traditional zinc-iodine flow battery (KI 3.0M, without additives) is lost. However, the capacity-voltage curve after adding the additive KSCN shows that the usable capacity is increased by one-third, reaching the theoretical capacity of 804mAh. The results of the examples demonstrate that the present invention, when used in a positive electrode electrolyte containing 3.0M iodine ion reactive material in a zinc-iodine flow battery, can increase the actual capacity by one-third compared to the traditional zinc-iodine flow battery.

[0116] The efficiency performance of the iodine-based flow battery prepared in Example 5 is as follows: Figure 12 As shown, the zinc-iodine flow battery with added additives can maintain a 99% coulombic efficiency while releasing the full capacity of iodine ions, and can stably cycle for more than 60 cycles with a capacity retention rate of over 99%. The results of the examples demonstrate that the present invention, when used in a positive electrode electrolyte containing 3.0M iodine ion reactive material, can achieve stable cycling in a zinc-iodine flow battery.

[0117] Figure 9 This is to highlight the effectiveness of 3.0 M KSCN in zinc-iodine flow batteries for 3.0 M I - The release of capacity, and Figure 12 This is to highlight that the additive of the present invention not only promotes 3.0M KSCN, but also... - The release of capacity, and the addition of ethanol, starch, defatted fiber, and carbon felt in the additives, ensures that the active substance content is 3.0 MI. - Stable cycling of zinc-iodine flow batteries.

[0118] Example 6,

[0119] The difference from Example 5 is that the KI molar concentration in the positive electrode electrolyte is 6.0 M.

[0120] The capacity and voltage of the iodine-based flow battery prepared in Example 6 are as follows: Figure 10As shown, comparing the capacity-voltage curves of zinc-iodine flow batteries with and without additives, it can be found that one-third of the capacity of the traditional zinc-iodine flow battery (KI 6.0M, without additives) is lost. However, the capacity-voltage curve after adding the additive KSCN shows that the usable capacity is increased by one-third, reaching the theoretical capacity of 1608mAh. The results of the examples demonstrate that the present invention, when used in a positive electrode electrolyte containing 6.0M iodine ion reactive material in a zinc-iodine flow battery, can increase the actual capacity by one-third compared to the traditional zinc-iodine flow battery.

[0121] Examples 4, 5, and 6, along with Examples 1, 2, and 3, serve to demonstrate the applicability of potassium thiocyanate in releasing iodide ion capacity. The iodide ion release effect of potassium thiocyanate is applicable not only to sulfur-iodine flow batteries (as in Examples 1, 2, and 3) but also to zinc-iodine flow batteries (as in Examples 4, 5, and 6).

[0122] Example 7,

[0123] The difference from Example 1 is that the Nafion membrane is replaced with a SPEEK membrane.

[0124] Capacity voltage such as Figure 13 As shown, when a SPEEK membrane is used as the separator in a sulfur-iodine flow battery, the addition of KSCN as an additive can achieve a capacity close to the theoretical capacity of 268mAh (with 1.0MI of positive electrode active material). - In contrast, traditional sulfur-iodine flow batteries lose one-third of their capacity. Examples demonstrate that the SPEEK separator can be used in the SCN of this invention. - A sulfur-iodine flow battery that uses iodine as a positive electrode additive to release its capacity.

[0125] Example 8,

[0126] The difference from Example 1 is that the Nafion membrane is replaced with an SPES membrane.

[0127] Capacity voltage such as Figure 14 As shown, when the sulfur-iodine flow battery uses a SPES membrane as the separator, the sulfur-iodine flow battery with added KSCN can achieve a capacity close to the theoretical capacity of 268mAh (positive electrode active material is 1.0MI). - In contrast, traditional sulfur-iodine flow batteries lose one-third of their capacity. Examples demonstrate that the SPES separator can be used in the SCN of this invention. - A sulfur-iodine flow battery that uses iodine as a positive electrode additive to release its capacity.

[0128] Example 9,

[0129] The difference from Example 4 is that the Nafion membrane is replaced with a PBI membrane.

[0130] Capacitance voltage, such as Figure 15 As shown, when a PBI membrane is used as the separator in a zinc-iodine flow battery, the zinc-iodine flow battery with the addition of KSCN can achieve a capacity close to the theoretical capacity of 268mAh (with 1.0MI of positive electrode active material). - In contrast, traditional zinc-iodine flow batteries lose one-third of their capacity. Examples show that the PBI separator can be used in the SCN of this invention. - Zinc-iodine flow batteries that release iodine capacity as a positive electrode additive.

[0131] Example 10,

[0132] The difference from Example 1 is that the positive electrode active material KI is replaced with NaI, the positive electrode supporting electrolyte KSCN is replaced with NaSCN, the negative electrode active material is replaced with Na2S (1M), and the alkaline solution for ionization treatment of the membrane is replaced with NaOH solution.

[0133] Capacitance voltage, such as Figure 16 As shown, when NaI is used as the positive electrode active material in a sulfur-iodine flow battery, the addition of KSCN as an additive can achieve a capacity close to the theoretical capacity of 268mAh (positive electrode active material is 1.0MI). - In contrast, traditional sulfur-iodine flow batteries lose one-third of their capacity. The results of these examples demonstrate that NaI can be used in the SCN of this invention. - A sulfur-iodine flow battery that uses iodine as a positive electrode additive to release its capacity.

[0134] Example 11,

[0135] The difference from Example 1 is that the positive electrode active material KI is replaced with LiI, the positive electrode supporting electrolyte KSCN is replaced with LiSCN, the negative electrode active material is replaced with Li2S (4.0M), and the alkaline solution for ionization treatment of the membrane is replaced with LiOH solution.

[0136] Capacitance voltage, such as Figure 17 As shown, when LiI is used as the positive electrode active material in a sulfur-iodine flow battery, the sulfur-iodine flow battery with added LiSCN can achieve a capacity close to the theoretical capacity of 268mAh (positive electrode active material is 1.0M). - While traditional sulfur-iodine flow batteries lose one-third of their capacity, the results of the examples show that LiI can be used in the SCN of this invention. - A sulfur-iodine flow battery that uses iodine as a positive electrode additive to release its capacity.

[0137] Example 12,

[0138] The difference from Example 1 is that the positive electrode active material KI (1.0M) is replaced with ZnI2 (0.5M), the positive electrode supporting electrolyte KSCN is replaced with Zn(SCN)2, and the alkaline solution for ionization treatment of the membrane is replaced with ZnCl2 (1M) solution.

[0139] Capacitance voltage, such as Figure 18 As shown, when ZnI2 is used as the positive electrode active material in a sulfur-iodine flow battery, the sulfur-iodine flow battery with added Zn(SCN)2 can achieve a capacity close to the theoretical capacity of 268mAh (positive electrode active material is 1.0MI). - While traditional sulfur-iodine flow batteries lose one-third of their capacity, the results of the embodiments show that ZnI2 can be used in the SCN of this invention. - A sulfur-iodine flow battery that uses iodine as a positive electrode additive to release its capacity.

[0140] Example 13,

[0141] The difference from Example 4 is that the positive electrode active material KI is replaced with NaI, the positive electrode supporting electrolyte KSCN is replaced with NaSCN, the negative electrode supporting electrolyte KBr is replaced with NaBr (2.0M), and the alkaline solution for ionization treatment of the membrane is replaced with NaOH (0.1M) solution.

[0142] Capacitance voltage, such as Figure 19 As shown, when NaI is used as the positive electrode active material in a zinc-iodine flow battery, the zinc-iodine flow battery with the addition of KSCN can achieve a capacity close to the theoretical capacity of 268mAh (positive electrode active material is 1.0MI). - In contrast, traditional zinc-iodine flow batteries lose one-third of their capacity. The results of these examples demonstrate that NaI can be used in the SCN of this invention. - Zinc-iodine flow batteries that release iodine capacity as a positive electrode additive.

[0143] Example 14,

[0144] The difference from Example 4 is that the positive electrode active material KI is replaced with NH4I, and the negative electrode supporting electrolyte KBr is replaced with NH4Br (3.0M).

[0145] Capacitance voltage, such as Figure 20 As shown, when NH4I is used as the positive electrode active material in a zinc-iodine flow battery, the zinc-iodine flow battery with the addition of KSCN can achieve a capacity close to the theoretical capacity of 268mAh (positive electrode active material is 1.0MI). - In contrast, traditional zinc-iodine flow batteries lose one-third of their capacity. Examples demonstrate that NH4I can be used in the SCN of this invention. - Zinc-iodine flow batteries that release iodine capacity as a positive electrode additive.

[0146] Example 15,

[0147] The difference from Example 4 is that the positive electrode active material KI is replaced with LiI, the positive electrode supporting electrolyte KSCN is replaced with LiSCN, the negative electrode supporting electrolyte KBr is replaced with LiBr (4.0M), and the alkaline solution for ionization treatment of the membrane is replaced with LiOH (10M) solution.

[0148] Capacitance voltage, such as Figure 21 As shown, when LiI is used as the positive electrode active material in a zinc-iodine flow battery, the zinc-iodine flow battery with added LiSCN can achieve a capacity close to the theoretical capacity of 268mAh (with a positive electrode active material of 1.0MI). - While traditional zinc-iodine flow batteries lose one-third of their capacity, the results of the examples show that LiI can be used in the SCN of this invention. - Zinc-iodine flow batteries that release iodine capacity as a positive electrode additive.

[0149] Example 16,

[0150] The difference from Example 4 is that the positive electrode active material KI (1.0M) is replaced with ZnI2 (0.5M), the positive electrode supporting electrolyte KSCN is replaced with Zn(SCN)2, and the negative electrode supporting electrolyte KBr is no longer added; since Zn is present in both the positive and negative electrode electrolytes... 2+ Zn 2+ Can replace K + The internal circuit loop is completed by using a diaphragm, eliminating the need to add an additional K. + Therefore, the negative electrode supporting electrolyte KBr is no longer added.

[0151] Capacitance voltage, such as Figure 22 As shown, when ZnI2 is used as the positive electrode active material in a zinc-iodine flow battery, the zinc-iodine flow battery with the addition of KSCN can achieve a capacity close to the theoretical capacity of 268mAh (positive electrode active material is 1.0MI). - In contrast, traditional zinc-iodine flow batteries lose one-third of their capacity. The results of these examples demonstrate that ZnI2 can be used in the SCN of this invention. - Zinc-iodine flow batteries that release iodine capacity as a positive electrode additive.

[0152] Example 17,

[0153] The difference from Example 1 is that the ethanol concentrations in the positive electrode electrolyte are 0.1%, 25%, and 50%, respectively. The positive electrode electrolyte is placed in a positive electrode storage tank, and volcanic rock wrapped in a fabric-like polyester fiber is added to the tank as the positive electrode electrolyte. The capacity and voltage can all reach the theoretical capacity of 268mAh, which is one-third higher than that of traditional sulfur-iodine flow batteries. Specifically, when the ethanol concentration is 0.1%, the capacity and voltage are as follows: Figure 23 As shown.

[0154] Example 18,

[0155] The difference from Example 1 is that the starch concentrations in the positive electrode electrolytes are 0.1%, 5%, and 10%, respectively. The positive electrode electrolytes are placed in a positive electrode storage tank, and graphite felt wrapped in acrylic fibers in a cloth-like structure is added to the tank as the positive electrode electrolyte. The capacity and voltage can all reach the theoretical capacity of 268mAh, which is one-third higher than that of traditional sulfur-iodine flow batteries. Specifically, the starch concentration is 5%, and the capacity and voltage are as follows... Figure 24 As shown.

[0156] Example 19,

[0157] The difference from Example 1 is that the concentration of sodium alginate in the positive electrode electrolyte is 10%, the positive electrode electrolyte is placed in the positive electrode storage tank, and a nickel mesh wrapped with cloth-like polyester fiber is added to the positive electrode storage tank as the positive electrode electrolyte of the battery.

[0158] Capacity voltage such as Figure 25 As shown, it achieves a theoretical capacity of 268mAh, which is one-third higher than the actual capacity of traditional sulfur-iodine flow batteries.

[0159] Example 20,

[0160] The difference from Example 1 is that the concentration of cyclodextrin in the positive electrode electrolyte is 0.1%, the positive electrode electrolyte is placed in the positive electrode storage tank, and activated carbon wrapped in cloth-like PP fibers is added to the positive electrode storage tank as the positive electrode electrolyte of the battery.

[0161] Capacity voltage such as Figure 26 As shown, it achieves a theoretical capacity of 268mAh. Compared to traditional sulfur-iodine flow batteries, the actual capacity can be increased by one-third.

[0162] Example 21,

[0163] The difference from Example 1 is that the chitosan concentration in the positive electrode electrolyte is 5%, the positive electrode electrolyte is placed in the positive electrode storage tank, and zeolite wrapped in cloth-like degreased cotton fibers is added to the positive electrode storage tank as the positive electrode electrolyte of the battery.

[0164] Capacity voltage such as Figure 27 As shown, it achieves a theoretical capacity of 268mAh, which is one-third higher than the actual capacity of traditional sulfur-iodine flow batteries.

[0165] Example 22,

[0166] The difference from Example 1 is that the concentration of metal-organic framework material UIO-66 in the positive electrode electrolyte is 10%, the positive electrode electrolyte is placed in the positive electrode storage tank, and zeolite wrapped in cloth-like degreased cotton fibers is added to the positive electrode storage tank as the positive electrode electrolyte of the battery.

[0167] Capacity voltage such as Figure 28 As shown, it achieves a theoretical capacity of 268mAh, which is one-third higher than the actual capacity of traditional sulfur-iodine flow batteries.

[0168] Comparative Example 1,

[0169] The difference from Example 1 is that KI and KBr are dissolved in water, with a KI molar concentration of 1.0 M and a KBr molar concentration of 3.0 M, and activated carbon is added as the positive electrode electrolyte of the battery.

[0170] In this embodiment, KI and KBr are used as the positive electrode electrolyte, K2S aqueous solution is used as the negative electrode electrolyte, carbon felt is used as the positive and negative electrode materials of the flow battery, and an ionized Nafion 212 membrane is used as the separator. The key materials are assembled into a sulfur-iodine flow battery, and the battery is tested using a Newway testing system. The charge / discharge current density is 20 mA cm⁻¹. -2 .

[0171] The capacity and voltage of the iodine-based flow battery prepared in Comparative Example 1 are as follows: Figure 29 As shown in the diagram, comparing the capacity-voltage graphs of the sulfur-iodine flow battery, it can be found that the capacity of the sulfur-iodine flow battery with added KBr is partially lost. Experimental results show that, in the sulfur-iodine flow battery of Example 1 of this invention, using a positive electrode electrolyte containing 1.0M iodine ion reactive material, compared to adding Br... - The (KBr) sulfur-iodine flow battery achieves better actual capacity release, and the positive electrode additive has a better capacity release effect for iodine ions.

[0172] The efficiency and capacity retention of the iodine-based flow battery prepared in Comparative Example 1 are as follows: Figure 30As shown in the comparison of the cycle performance graphs of sulfur-iodine flow batteries, it can be found that the sulfur-iodine flow battery with KBr and activated carbon as additives is unstable during cycling; while the sulfur-iodine flow battery with the additive of the present invention (Example 1: a solution with KSCN molar concentration of 3.0M, ethanol concentration of 10%, and starch concentration of 1%) can stably cycle for more than 80 charge-discharge tests. The results of these examples demonstrate that, under the same battery materials and assembly technology, the cathode additive of the present invention is superior to bromide ions and activated carbon in maintaining the cycle stability of high-energy-density iodine-based flow batteries.

[0173] Comparative Example 2,

[0174] The difference from Example 1 is that the ethanol concentration in the positive electrode electrolyte is 75%. When the ethanol concentration is too high, ethanol will cause degradation of the separator inside the battery. The separator will not be able to prevent cross-contamination of the positive and negative electrode active materials, resulting in battery failure.

[0175] Comparative Example 3,

[0176] The difference from Example 1 is that the starch concentration in the positive electrode electrolyte is 15%. Because too much starch is added per unit volume, the iodine positive electrode electrolyte cannot circulate normally. Excessive starch concentration leads to excessive positive electrode electrolyte concentration, resulting in high internal resistance and significant battery polarization, preventing the battery from undergoing normal charge-discharge cycles.

[0177] Prior art 1 (US11177476B2) introduces an adsorbent, polyethylene glycol (PEG), and bromide salt into the electrolyte, where the three substances synergistically release I... - Capacity. During battery charging, the adsorbent and PEG immobilize solid iodine in the electrolyte, while during discharge, the Br in the bromide salt... - Solid iodine is dissolved to allow it to participate in the discharge reaction; however, the assembled battery is difficult to cycle stably.

[0178] Comparison of the technical effects of the embodiments of the present invention with prior art 1 (US11177476B2):

[0179] In the prior art 1, F - ,Br - Cl - At - Various substances such as PVP are added to the iodine cathode. Through a complexation reaction with elemental iodine, a product of oxidation, they form I₂·X, unlocking the iodide ion capacity. However, because the complexation reaction between the additives and elemental iodine is slow, their ability to compete with iodide ions for elemental iodine is weak. The rate of iodine formation is much greater than the rate of the complexation reaction, and some iodine remains unreacted. - It reacts with the oxidation product I2 to form I3. - Unable to provide capacity, causing I -Capacity loss occurs because the additives complex with some iodine to form I₂·X, resulting in a large amount of iodine depositing on the electrode surface and increasing the battery's internal resistance. Furthermore, existing technology 1 only designs voltage control for testing the assembled battery, which can easily lead to incomplete oxidation of iodine ions during charging before reaching the cutoff voltage, resulting in ineffective utilization of iodine ions and significant capacity loss.

[0180] As in prior art 1 Figure 4 As shown, zinc-iodine batteries using 1.5M, 3.5M, and 5M ZnI2 as the positive electrode active material, with the addition of Br... - When used as an additive, it only reaches 32 Ah L. -1 58Ah L -1 87Ah L -1 The theoretical two-sided volumetric capacity should be 40.2 Ah L. -1 94Ah L -1 132Ah L -1 ), which are only 79%, 61%, and 66% of the theoretical capacity; as in prior art 1 Figure 11 As shown, a zinc-iodine battery using 4M ZnI2 as the positive electrode active material, with Br added to the positive electrode. - When using PVP and activated carbon, the efficiency is less than 87.5 Ah / L. -1 The theoretical two-sided volumetric capacity should be 107.2 Ah L. -1 Existing technology 1 adds Br to the positive electrode side. - Neither PVP nor activated carbon unlocked the full capacity of iodine ions on the positive electrode side; therefore, the aqueous iodine-based flow battery assembled in prior art 1 does not achieve effective utilization of iodine ions. For example, prior art 1... Figure 7 As shown, the lithium-iodine battery using 2.5M LiI as the positive electrode active material only achieves 53 Ah / L. -1 The theoretical one-sided volumetric capacity should be 67 Ah L. -1 The capacity is only 79% of the theoretical capacity; therefore, the non-aqueous iodine-based flow battery assembled by the existing technology 1 has not achieved effective utilization of iodine ions.

[0181] The embodiments of the present invention are in 1M I - When used as the positive electrode active material, the single-sided volumetric capacity of both the assembled sulfur-iodine flow battery and the zinc-iodine flow battery reached 26 Ah / L. -1 Potassium thiocyanate for I - The capacity release effect reached 100%, reaching I - The effect of fully releasing the theoretical capacity; fully released iodine-based flow battery I -While increasing capacity, the volumetric capacity was further improved, while ensuring the reversibility and stability of the battery. The iodine-based flow battery cycled stably under different current densities. The sulfur-iodine flow battery assembled in this embodiment of the invention achieved stable cycling at 10 mA cm⁻¹. -2 ~50mA cm -2 At a current density of 50 mA / cm², the coulombic efficiency can be stably maintained at 99%, and the efficiency can be maintained evenly at a current density of 50 mA / cm². -2 Switch back to 10mA cm -2 At that time, the battery's various efficiencies also returned to their initial state. At 20mA cm -2 At the specified current density, the sulfur-iodine battery can stably cycle 90 times, further demonstrating the battery's stability.

[0182] In the sulfur-iodine flow battery and zinc-iodine flow battery assembled in the embodiments of the present invention, potassium thiocyanate is used to treat I - The capacity release effect reached 100%, while in existing zinc-iodine batteries, bromide ions against I... - The capacity release efficiency is only 80% in lithium-iodine batteries; bromide ions in lithium-iodine batteries have a significant impact on I... - The capacity release effect was only 79%.

[0183] In 1M I - When used as the positive electrode active material, the single-sided volumetric capacity of both the sulfur-iodine flow battery and the zinc-iodine flow battery in the embodiments of the present invention reached 26 Ah / L. -1 It reached I - The theoretical capacity is fully released, while the single-sided volumetric capacity of existing zinc-iodine and lithium-iodine batteries is only 21 Ah / L. -1 The sulfur-iodine battery and zinc-iodine battery assembled in the embodiments of the present invention maintain a stable coulombic efficiency of 99% and can cycle stably for 90 cycles, while the zinc-iodine battery assembled in the prior art 1 has a coulombic efficiency of only 94% and can only cycle for 50 cycles.

[0184] The zinc-iodine flow battery assembled in Example 4 was subjected to polarization testing, such as... Figure 31 As shown, at 310mA cm -2 At that time, the zinc-iodine flow battery achieved a maximum power density of 206.2 mW / cm². -2 The embodiments of the present invention can achieve a higher power density of 206.2 mW / cm². -2 (at 310mA cm) -2 At times, such as Figure 31 As shown in the figure, the highest power density of the existing technology 1 is only 50mW / cm². -2 (at 70mA cm) -2 At that time, see the prior art 1 Figure 6 ).

[0185] Embodiment 4 of the present invention can adapt to current densities up to 20 mA cm⁻¹ -2 The current density of existing technology is only 10 mA / cm². -2 The embodiments of the present invention achieve a coulombic efficiency of up to 99% at 100% SOC and higher current density. Figure 8 , Figure 11 In contrast, existing technology 1 suffers from low current density, a state of charge (SOC) of only 70%, and a coulombic efficiency of only 95%. The embodiments of this invention achieve a higher single-sided volumetric density of 159.4 Ah / L. -1 (6.0M KI, such as) Figure 8 (As shown), while the highest energy density of existing technology 1 is only 101 Wh / L. -1 (5M ZnI2).

[0186] The embodiments of the present invention can unlock an additional 1 / 3 of the iodine ion capacity, enabling the effective utilization of all iodine ions at the positive electrode, while the prior art still loses some iodine ions, failing to achieve maximum utilization of iodine ions at the positive electrode. As shown in the embodiments of the present invention... Figure 1 , 2 As shown in Figures 3, 8, 9, and 10, embodiments of the present invention utilize 1.0M, 3.0M, and 6.0M. - The single-sided volumetric capacity of both the sulfur-iodine flow battery and the zinc-iodine flow battery reached nearly 26.8 Ah / L. -1 80.4Ah L -1 160.8Ah L -1 The theoretical capacity was increased by one-third, effectively improving the utilization rate of iodine ions.

[0187] In Example 3 of this invention, the iodine ion capacity unlocking rate in the sulfur-iodine flow battery reached 99.04% (6.0 M KI), and the iodine ion capacity unlocking rate in the zinc-iodine flow battery reached 99.03% (6.0 M KI).

[0188] In the embodiments of this invention, the selection and processing of key materials such as the separator, electrodes, and electrolyte of the iodine-based flow battery are functionally closely related; SCN - When added to the positive electrode iodine solution, during battery charging, thiocyanate (SCN) ions... - It combines with the iodine product formed by the oxidation reaction to form "[I₂SCN]". - ", then SCN - Make "[I2SCN]" - The covalent bonds of I2 in the middle break to form "SCN". - ·2I - Finally, "SCN" - ·2I - "It can recombine with elemental iodine to form "SCN" - ·I3- Thiocyanate (SCN) - SCN can continuously complex with elemental iodine (I₂). The complexation reaction is rapid and occurs before the iodide ion complexes with the reaction product elemental iodine. - This method can replace 1 / 3 of the reaction between iodine ions and the oxidation product iodine to unlock the iodine ion capacity. The above reaction process promotes further dissolution of iodine, preventing iodine precipitation in the electrode, reducing battery polarization, promoting catalytic reactions on the positive electrode, and improving the stability of the flow battery. Simultaneously, this embodiment of the invention adds thiocyanate, ethanol, adsorbent, three-dimensional porous material, and sieve filter material to the positive electrode electrolyte to fix the positive electrode active material. Ethanol promotes the dissolution of iodine, ensuring the circulation of the positive electrode electrolyte; and the sieve filter material is wrapped on the surface of the three-dimensional porous material and placed in the positive electrode electrolysis tank. This not only adsorbs the active material and reduces its permeation, but also prevents large insoluble particles from entering the battery, solving the problem of blockage in the positive electrode electrolyte flow channels. Iodine molecules are dissolved by ethanol because they are polarized by the hydroxyl groups (-OH) of ethanol; adsorbents and three-dimensional porous materials can adsorb positive electrode active materials due to their porous structure, thus reducing cross-contamination of active materials; sieving and filtering materials and three-dimensional porous materials block insoluble matter through pore size sieving, ensuring the circulation of positive electrode electrolyte. Assembling an iodine-based flow battery only requires one Nafion 212 membrane, which minimizes technical difficulty and greatly reduces battery cost.

[0189] This invention uses deionized water as the solvent for both the positive and negative electrode electrolytes. While maintaining low cost, this reduces the corrosive effect of the solvent on battery materials (electrodes, separators, etc.) and improves the battery's cycle performance. A highly selective ion exchange membrane is selected as the separator, reducing cost while improving ion selectivity, thus reducing battery polarization and further enhancing battery performance. Highly catalytically active carbon felt is used as the positive and negative electrodes, and highly conductive graphite plates are used as electron current collectors. These economical and practical materials complete the battery circuit. A silicone pad buffers the various materials and seals the electrolyte. Steel plates and screws provide structural support as the battery frame. Various economical and high-performance materials are used to assemble the iodine-based redox flow battery, such as sulfur-iodine batteries, zinc-iodine batteries, or aqueous organic iodine-based batteries. This reduces cost while improving the electrochemical performance of the iodine-based flow battery, assisting in the release of iodine ions (I₂O₃) from thiocyanate. - This invention improves the capacity and electrochemical performance of iodine-based flow batteries. The embodiments of this invention employ dual-condition control of voltage and theoretical capacity in the assembled battery, which maximizes the release of iodine ion capacity while avoiding side reactions, ensuring the reversibility of redox reactions, and guaranteeing stable charge-discharge cycle testing of the battery.

[0190] In summary, the positive electrode electrolyte of the iodine-based redox flow battery of the present invention can fully release the capacity of iodine ions, clear the electrolyte circulation channel, and prevent the penetration of active materials, thereby obtaining a high energy density, low cost, and long life iodine-based flow battery.

[0191] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A high energy density low cost iodine based flow battery comprising positive and negative electrolytes, positive and negative electrodes, a separator, electrolyte tanks, circulating pumps, characterized in that, The active material in the positive electrode electrolyte is iodide, and the additives include thiocyanate, ethanol, adsorbent, three-dimensional porous material, and sieving and filtration material. The cations of thiocyanate and iodide are the same. − With SCN − The molar ratio is 1.0~6.0:3.0; the ethanol concentration is 0.1~50%, the adsorbent concentration is 0.1~10%, and the sieve filter material is wrapped on the surface of the three-dimensional porous material; The active substance of the negative electrode electrolyte is any one of sulfide, zinc salt, lithium salt, magnesium salt, aluminum salt, anthraquinone-2,7-disulfonic acid disodium salt or 12-phosphotungstic acid, with a molar concentration of 1~8.0M. The diaphragm is an ion exchange membrane that has undergone ionization treatment; The positive and negative electrodes are graphite felt or carbon felt.

2. The high energy density, low cost iodine-based flow battery of claim 1, wherein, The iodide is any one of KI, NaI, LiI, or ZnI2, and the thiocyanate is any one of NaSCN, KSCN, LiSCN, or Zn(SCN)2. The positive electrode electrolyte contains I... − Molar concentrations range from 1.0 M to 6.0 M, SCN − The molar concentration is 3.0 M.

3. The high energy density, low cost iodine-based flow battery of claim 1, wherein, The adsorbent is starch, cyclodextrin, alginate, chitosan, metal-organic framework materials, covalent-organic framework materials, or zeolite imidazole ester framework materials.

4. The high energy density, low cost iodine-based flow battery of claim 1, wherein, The three-dimensional porous material is any one of carbon felt, graphite felt, nickel mesh, activated carbon, zeolite, or volcanic rock.

5. The high energy density, low cost iodine-based flow battery of claim 1, wherein, The screening and filtering material is any one of PP fiber, polyester fiber, degreased cotton fiber or acrylic fiber in the form of cloth, and the screening and filtering material is wrapped on the surface of a three-dimensional porous material.

6. The high energy density, low cost iodine-based flow battery of claim 1, wherein, The sulfide is any one of K2S, Na2S or Li2S; the zinc salt is ZnI2, ZnBr2 or ZnCl2; the lithium salt is LiI, LiBr or LiCl; the magnesium salt is MgI2, MgBr2 or MgCl2; and the aluminum salt is AlI3, AlCl3 or AlBr3.

7. The high energy density, low cost iodine-based flow battery of claim 1, wherein, The supporting electrolyte of the negative electrode electrolyte is any one of KI, KBr, KCl, NaI, NaBr, NaCl, NH4I, NH4Br, NH4Cl, LiI, LiBr, or LiCl. The active material and supporting electrolyte of the negative electrode electrolyte are the same as the cations of the active material of the positive electrode. The concentration range of the supporting electrolyte of the negative electrode electrolyte is 0.0~4.0M.

8. The high energy density, low cost iodine-based flow battery of claim 1, wherein, The ion exchange membrane is any one of Nafion membrane, SPEEK membrane, SPES membrane or PBI membrane.

9. The method of producing a high energy density, low cost iodine-based flow battery of claim 1, wherein, Please follow these steps: S1. Prepare a strong base solution in a beaker using deionized water, with a molar concentration of 0.1~10M; S2, Preparation of the diaphragm: The ion exchange membrane is immersed in deionized water for cleaning; S3, Immerse the cleaned ion exchange membrane in the alkaline solution prepared in step S1 for ionization treatment; the ionization temperature is 50~100℃ and the time is 1~3h. S4. Wash the membrane repeatedly with deionized water until the solution pH = 6~7, then soak it in deionized water for use as an ion exchange membrane. S5, Preparation of positive electrode electrolyte: Prepare an iodide solution using deionized water, and add thiocyanate as an additive. − Molar concentrations range from 1.0 M to 6.0 M, SCN − The molar concentration is 3.0 M; the iodide is KI, NaI, LiI or ZnI2, and the thiocyanate is NaSCN, KSCN, LiSCN or Zn(SCN)2; the adsorbent is starch, cyclodextrin, alginate, chitosan, metal-organic framework materials, covalent-organic framework materials or zeolite imidazole ester framework structure materials; the three-dimensional porous material is carbon felt, graphite felt, nickel mesh, activated carbon, zeolite or volcanic rock; the sieving and filtering material is PP fiber, polyester fiber, degreased cotton fiber or acrylic fiber; S6, Preparation of negative electrode electrolyte: The negative electrode active material is prepared with deionized water, and the ion concentrations on both the positive and negative electrodes are the same. S7 uses graphite felt or carbon felt as the positive and negative electrodes of the battery. S8. Assemble the membrane, positive electrolyte, negative electrolyte, and positive and negative electrodes prepared in steps S4, S5, S6, and S7 into an iodine-based flow battery.

10. The method of claim 9, wherein the high energy density low cost iodine-based flow battery is prepared by the steps of: In step S1, the strong alkali solution is an aqueous solution of KOH, NaOH, or LiOH.

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