An alkaline nickel-sulfur flow battery and a method of making the same

Abstract

The application discloses a kind of the alkaline nickel sulfur liquid flow battery, including positive electrode, negative electrode, diaphragm and electrolyte, the active substance of the positive electrode is nickel hydroxide, the active substance of the negative electrode is the polysulfide containing S2 2‑ / 2‑ ;The diaphragm is cation exchange membrane, the electrolyte is alkaline aqueous solution, and the positive electrode and negative electrode select sodium hydroxide or potassium hydroxide as supporting electrolyte.Because nickel hydroxide is used on the positive electrode side, the reaction on the positive electrode side is solid to solid in full solid phase, so that there is no phase change reaction on one side of the electrode, and the other side is only the electrochemical oxidation-reduction reaction of liquid active ion, so there is no dendrite phenomenon.The liquid active substance is sulfide anion, so even the most commonly used cation exchange membrane also has excellent blocking characteristics.The aqueous solution containing hydroxide is used as the supporting electrolyte, the viscosity is significantly reduced, so the pump power loss is greatly reduced under the same flow.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to an alkaline nickel-sulfur flow battery and its preparation method. Background Technology

[0002] With the increasing depletion of traditional fossil fuels and the serious environmental pollution they cause, finding and developing new energy sources is imperative. However, renewable energy sources such as wind and solar power are highly volatile and intermittent, and direct grid connection will impact the power grid. Generally, a 10%-15% energy storage system is needed as a buffer. As the proportion of renewable energy in the power system further increases, the required proportion and scale of energy storage will gradually increase. Currently, pumped hydro storage systems, which have the largest installed capacity, are experiencing slower development due to geographical location and geological requirements. Lithium-ion batteries, which account for the largest share of electrochemical energy storage, are also facing limitations due to their poor safety and the continuously rising price of lithium carbonate, a raw material. As a new type of large-scale energy storage system, flow batteries, with their intrinsic safety, scalability, and fast response, have gradually attracted widespread attention worldwide. Developing intrinsically safe and inexpensive flow battery systems meets the needs of both the energy storage industry and the national dual-carbon strategy.

[0003] In flow batteries, the most mature systems currently available are vanadium-based, iron-chromium, and zinc-bromine systems. However, the refining process for vanadium salts is extremely complex and expensive; the cost of the active material in the electrolyte for vanadium batteries is approaching 1800 yuan / kWh, comparable to the cost of lithium iron phosphate battery systems. Another relatively mature electrolyte system for flow batteries is the iron-chromium electrolyte. While its cost is lower, its energy density is limited by the solubility of ferrous ions, which is low, and it suffers from chromium aging and hydrogen evolution, severely hindering its commercialization. Furthermore, both types of flow batteries use cations as the reactive ions, while most current separators are cation exchange membranes. The anionic functional groups on cation exchange membranes attract positively charged cations, making cross-diffusion contamination between the positive and negative electrolytes highly likely, leading to rapid performance degradation. In the zinc-bromine system, the presence of zinc dendrites on the negative electrode side can cause the zinc dendrites to pierce the separator after a certain number of charge-discharge cycles, leading to mixing of the positive and negative electrode active materials and limiting its cycle life.

[0004] In summary, there is an urgent need to develop a new electrolyte system for flow batteries that is high-performance, low-cost, easy to prepare, has high energy density, and is economically competitive. Summary of the Invention

[0005] To address the problems in related technologies, this invention proposes an alkaline nickel-sulfur flow battery and its preparation method.

[0006] The technical solution of this invention is implemented as follows:

[0007] According to one aspect of the present invention, an alkaline nickel-sulfur flow battery is provided.

[0008] This alkaline nickel-sulfur flow battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The active material of the positive electrode is nickel hydroxide, and the active material of the negative electrode contains S2. 2- / S 2- The membrane is a cation exchange membrane, the electrolyte is an alkaline aqueous solution, and the positive and negative electrodes are selected as supporting electrolytes, namely sodium hydroxide or potassium hydroxide.

[0009] Preferably, it contains S2 2- / S 2- The polysulfides are sodium polysulfide or potassium polysulfide.

[0010] Preferably, the cation exchange membrane is a perfluorosulfonic acid membrane.

[0011] Preferably, the electrolyte contains potassium or sodium ions at a molar concentration of 1-9 mol / L, hydroxide ions at a molar concentration of 1-6 mol / L, and sulfide ions at a molar concentration of 1-3 mol / L.

[0012] Preferably, the active material carriers of both the positive and negative electrodes are nickel meshes.

[0013] Preferably, both the positive and negative current collectors are flexible graphite.

[0014] According to another aspect of the present invention, a method for preparing an alkaline nickel-sulfur flow battery is provided.

[0015] The preparation method of this alkaline nickel-sulfur flow battery includes the following steps:

[0016] A slurry containing nickel hydroxide powder, activated carbon conductive agent, and binder is uniformly mixed and then coated onto a nickel mesh.

[0017] Sodium hydroxide or potassium hydroxide is dissolved in an aqueous solution to form an alkaline solution, and this alkaline solution is added to the positive electrode cavity;

[0018] Sodium sulfide is dissolved in an aqueous solution with sodium hydroxide or potassium hydroxide to form a sodium sulfide aqueous solution, and solid sulfur particles are dissolved in the sodium sulfide aqueous solution to form a negative electrode electrolyte.

[0019] The negative electrode electrolyte and the pre-prepared nickel mesh are added to the negative electrode cavity.

[0020] In addition, the preparation method of the alkaline nickel-sulfur flow battery also includes: pre-treating the nickel mesh to promote the formation of a nickel sulfide layer on the surface of the nickel mesh.

[0021] The pretreatment of the nickel mesh to promote the formation of a nickel sulfide layer on the surface includes: cleaning the nickel mesh in acetone and hydrochloric acid to remove surface oil stains and oxides; washing the cleaned nickel mesh with water and drying it; and boiling the dried nickel mesh in a potassium disulfide or sodium disulfide solution until the surface color changes from silver to black, forming a dense nano-flower-like nickel sulfide layer.

[0022] Preferably, the molar concentration of potassium disulfide is 1 mol / L, and the boiling time is 4-5 h.

[0023] Beneficial effects:

[0024] Because a nickel hydroxide (Ni(OH)₂ / NiOOH) redox couple is used on the positive electrode side, the reaction on the positive electrode side is a solid-to-solid reaction, resulting in no phase transition reaction on one side of the electrode and only an electrochemical redox reaction of liquid active ions on the other side. Therefore, there is no phase transition reaction and no dendrite formation. Furthermore, the liquid active material is a sulfide anion, which exhibits excellent barrier properties even with the most commonly used commercial cation exchange membranes. Using an aqueous solution containing dissolved hydroxide as the supporting electrolyte significantly reduces viscosity compared to the sulfuric acid electrolyte in vanadium redox flow batteries, thus greatly reducing pump power loss at the same flow rate.

[0025] Furthermore, the alkaline nickel-sulfur flow battery described in this invention is inexpensive, costing only about 1 / 6 of the price of a traditional vanadium redox flow battery. It boasts a high output voltage of 0.91V and a wide operating range, functioning within -15 to 60°C, making it suitable for the climate requirements of most regions in my country. In contrast, traditional vanadium redox flow batteries operate only within a temperature range of 10-40°C. When the battery temperature exceeds 40°C, a cooling system is required to prevent V₂O₅ precipitation on the positive electrode side. However, the cooling system itself is expensive and consumes electricity, reducing the overall system efficiency and limiting its application. In contrast, the flow battery of this invention increases electrolyte conductivity and reaction kinetics with increasing temperature. When the temperature is below 60°C, no cooling system is needed, truly achieving wide-temperature operation. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments 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.

[0027] Figure 1 This is a schematic diagram of the structure of an alkaline nickel-sulfur flow battery according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic flowchart of the preparation method of an alkaline nickel-sulfur flow battery according to an embodiment of the present invention;

[0029] Figure 3 These are electron microscope images of the original electrode and the electrode loaded with nickel sulfide according to an embodiment of the present invention.

[0030] Figure 4 This is an elemental analysis energy spectrum of an electrode carrying nickel sulfide according to an embodiment of the present invention;

[0031] Figure 5 This is a potential diagram of the positive and negative electrodes of an alkaline nickel-sulfur flow battery according to an embodiment of the present invention;

[0032] Figure 6 This is a 20-cycle charge-discharge curve of an alkaline nickel-sulfur flow battery according to an embodiment of the present invention;

[0033] Figure 7 This is a 500-cycle charge-discharge curve of an alkaline nickel-sulfur flow battery according to an embodiment of the present invention;

[0034] Figure 8 This is a potential diagram of nickel sulfide catalyst on the negative electrode side of an alkaline nickel-sulfur flow battery according to an embodiment of the present invention.

[0035] Figure 9 This is a potential diagram of polysulfides on a graphite electrode according to an embodiment of the present invention;

[0036] Figure 10 This is a potential diagram of polysulfides on a manganese dioxide electrode according to an embodiment of the present invention;

[0037] Figure 11 This is a potential diagram of polysulfides on a titanium nitride electrode according to an embodiment of the present invention.

[0038] In the picture:

[0039] 1. Positive electrode current collector; 2. Positive electrode active material; 3. Positive electrode electrolyte; 4. Diaphragm; 5. Negative electrode electrolyte; 6. Negative electrode active material; 7. Negative electrode current collector; 8. Negative electrode electrolyte storage tank; 9. Negative electrode electrolyte pipeline; 10. Negative electrode electrolyte drive pump. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0041] According to an embodiment of the present invention, an alkaline nickel-sulfur flow battery and a method for preparing the same are provided.

[0042] like Figure 1 As shown, an alkaline nickel-sulfur flow battery according to an embodiment of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte. The active material of the positive electrode is nickel hydroxide (Ni(OH)2 / NiOOH), and the active material of the negative electrode is an electrolyte containing S2. 2- / S 2- The membrane is a cation exchange membrane, the electrolyte is an alkaline aqueous solution, and the positive and negative electrodes are selected as supporting electrolytes, namely sodium hydroxide or potassium hydroxide.

[0043] In one specific embodiment, S2 is included. 2- / S 2- The polysulfides are sodium polysulfide or potassium polysulfide. The cation exchange membrane is a perfluorosulfonic acid membrane. The electrolyte contains potassium or sodium ions at a molar concentration of 1-9 mol / L, hydroxide ions at a molar concentration of 1.0-6.0 mol / L, and sulfide ions at a molar concentration of 1-3 mol / L. The active materials of both the positive and negative electrodes are supported by nickel mesh. The current collectors of both the positive and negative electrodes are flexible graphite.

[0044] like Figure 2 As shown, a method for preparing an alkaline nickel-sulfur flow battery according to an embodiment of the present invention includes the following steps:

[0045] Step S201: Mix the powder containing nickel hydroxide, activated carbon conductive agent and binder evenly to form a slurry, and coat the slurry onto the nickel mesh;

[0046] Step S203: Dissolve sodium hydroxide or potassium hydroxide in an aqueous solution to form an alkaline solution, and add the alkaline solution into the positive electrode cavity;

[0047] Step S205: Dissolve sodium sulfide and sodium hydroxide or potassium hydroxide in an aqueous solution to form a sodium sulfide aqueous solution, and dissolve solid sulfur particles in the sodium sulfide aqueous solution to form a negative electrode electrolyte;

[0048] Step S207: Add the negative electrode electrolyte and the pre-prepared nickel mesh into the negative electrode cavity.

[0049] In one embodiment, the method for preparing the alkaline nickel-sulfur flow battery further includes: pre-treating the nickel mesh to induce the formation of a nickel sulfide layer on the surface of the nickel mesh. The pre-treatment of the nickel mesh to induce the formation of the nickel sulfide layer includes: cleaning the nickel mesh in acetone and hydrochloric acid to remove surface oil and oxides; washing the cleaned nickel mesh with water and drying it; and boiling the dried nickel mesh in a 1 mol / L potassium disulfide solution for 4-5 hours until the surface color changes from silver to black, forming a dense, nano-flower-like nickel sulfide layer.

[0050] In practical applications, the alkaline nickel-sulfur flow battery of the present invention can use the flow mode only on the negative electrode side. The nickel hydroxide (Ni(OH)2) / NiOOH reduction couple is used on the positive electrode side, while the sulfide couple S 2- / S2 2- The active material is used on the negative electrode side.

[0051] Continue to refer to Figure 1 The alkaline nickel-sulfur flow battery includes an electrochemical reaction section, a negative electrode reservoir, a negative electrode electrolyte, a negative electrode, an ion exchange membrane, a positive electrode, a positive electrode electrolyte, positive and negative electrode current collectors, positive and negative electrode pipelines, and a drive device. Both the positive and negative electrode electrolytes contain hydroxide as a supporting electrolyte. During battery operation, the active material on the negative electrode side is pumped into the porous electrode and circulates within its respective reaction chamber, undergoing an electrochemical oxidation-reduction reaction on the porous electrode surface to store and release electrical / chemical energy. The positive and negative half-cells are separated into independent positive and negative electrode sides by a separator, each forming a closed loop with the electrolyte reservoirs on both sides. The positive electrode side active material of this invention undergoes a solid-to-solid transition and does not involve a phase change, making it a single-sided flow battery.

[0052] During charging, the positive electrode side cavity remains stationary, and the nickel hydroxide on the nickel mesh surface is oxidized to nickel hydroxide. The negative electrode active material is transported from the negative electrode reservoir to the negative electrode cavity, S2. 2- Reduced to S 2- Both are ions in a dissolved state; the process is reversed during discharge.

[0053] The negative electrode involved in this invention can be made more reactive by the following methods: (1) the nickel mesh is first cleaned in acetone and hydrochloric acid to remove surface oil and oxides; (2) the cleaned nickel mesh is washed with water and then dried; (3) the nickel mesh is then boiled in a 1 mol / L K2S2 solution for 4 to 5 hours until the surface color changes from silver to black, forming a dense nano-flower-like nickel sulfide layer. The electrode is then stored in an atmosphere containing a protective gas. Electron micrographs of the original electrode and the electrode loaded with nickel sulfide are shown below. Figure 3As shown (where ab is the original nickel mesh and cd is the nickel mesh loaded with nickel sulfide), after treatment, a catalytic layer is attached to the electrode surface, thereby significantly improving the active sites and catalytic activity of the reaction. The elemental analysis energy dispersive spectroscopy (EDS) experiments of the electrode loaded with nickel sulfide are shown below. Figure 4 As shown, after treatment, sulfur on the electrode surface can be uniformly distributed on the nickel electrode surface, proving that this method can uniformly achieve the preparation and treatment of large-scale electrodes.

[0054] Batteries equipped with the aforementioned electrodes exhibit excellent performance. The flow battery of this invention boasts extremely high sulfide solubility, reaching 5 mol / L. Based on the electrolyte at the negative electrode, the theoretical energy density reaches 130 Wh / L, significantly higher than common vanadium redox flow batteries (35 Wh / L) and iron-chromium flow batteries (20 Wh / L). Furthermore, both the positive and negative electrodes possess excellent electrochemical reduction activity, low cost, and stability. The rational selection of the alkaline nickel-sulfur flow battery stack allows the standard output voltage to reach 0.93 V, the operating current density to reach 50 mA cm⁻², and the charge-discharge energy efficiency to remain above 82%. The electrochemical performance of the alkaline nickel-sulfur flow battery far surpasses that of other existing alkaline flow battery systems. Compared to existing flow battery systems, it combines the advantages of high energy density and low cost, demonstrating promising commercial application prospects.

[0055] In practical applications, the alkaline nickel-sulfur flow battery is actually fabricated as follows:

[0056] Step 1: Preparation of active materials: Positive electrode: Ni(OH)2 powder, activated carbon, Nafion binder, 3M KOH solution; Negative electrode: 5M Na2S2 solution, 3M KOH solution. Figure 5 As shown, cyclic voltammetry was used to detect the active materials of the positive and negative electrodes. The redox peak on the right represents the nickel hydroxide electrode, and the redox peak on the left represents the electrochemical performance of the polysulfide active material on a NiS-supported nickel grid. Step 2: Battery assembly; see [link to single-cell structure and system diagram]. Figure 1 From right to left, the components are: negative electrode current collector (flexible graphite), negative electrode (nickel mesh loaded with nickel sulfide), separator (Nafion), positive electrode (nickel mesh loaded with Ni(OH)2), and positive electrode current collector. Step 3: Battery testing. At room temperature, the battery is charged and discharged at a constant current density of 100 mA / cm² for 20 cycles, and the charge / discharge curve is as follows. Figure 6 As shown; among them, the capacity retention rate after 500 cycles is still as high as 72%, which is far higher than other types of flow batteries (all-vanadium, iron-chromium, zinc-bromine, etc.), such as Figure 7 As shown.

[0057] like Figure 8As shown, when nickel sulfide is deposited on the surface of the nickel mesh, obvious redox peaks appear, indicating that nickel sulfide has good catalytic activity for the reaction of polysulfides (under alkaline conditions). However, when the active material is pure nickel mesh, almost no redox peaks are observed.

[0058] like Figure 9-11 The figures show the redox peaks of polysulfides on the surfaces of graphite, manganese dioxide, and TiN electrodes, respectively. Analysis reveals that, compared to the nickel grid supported on the nickel sulfide catalyst mentioned in this invention, other electrodes and catalysts exhibit larger gaps between oxidation and reduction peaks (poor reversibility, and significant polarization during charge / discharge). Furthermore, electrodes such as titanium nitride show a significant increase in peak potential difference and a decrease in peak current after only two cycles, indicating poor electrode stability. These electrodes cannot remain stable in the alkaline redox reaction of polysulfides.

[0059] By employing the above-described technical solution of this invention, a nickel hydroxide (Ni(OH)₂ / NiOOH) redox couple is used on the positive electrode side. Therefore, the reaction on the positive electrode side is a solid-to-solid reaction, resulting in no phase transition reaction on one side of the electrode and only an electrochemical oxidation-reduction reaction of liquid active ions on the other side. Thus, dendrite formation is absent. Furthermore, the liquid active material is a sulfide anion, which exhibits excellent barrier properties even with the most commonly used commercial cation exchange membranes. Using an aqueous solution containing dissolved hydroxide as the supporting electrolyte significantly reduces viscosity compared to the sulfuric acid electrolyte in vanadium redox flow batteries, thereby greatly reducing pump power loss at the same flow rate.

[0060] Furthermore, the alkaline nickel-sulfur flow battery described in this invention is inexpensive, costing only about 1 / 6 of the price of a traditional vanadium redox flow battery. It boasts a high output voltage of 0.91V and a wide operating range, functioning within -15 to 60°C, making it suitable for the climate requirements of most regions in my country. In contrast, traditional vanadium redox flow batteries operate only within a temperature range of 10-40°C. When the battery temperature exceeds 40°C, a cooling system is required to prevent V₂O₅ precipitation on the positive electrode side. However, the cooling system itself is expensive and consumes electricity, reducing the overall system efficiency and limiting its application. In contrast, the flow battery of this invention increases electrolyte conductivity and reaction kinetics with increasing temperature. When the temperature is below 60°C, no cooling system is needed, truly achieving wide-temperature operation.

[0061] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An alkaline nickel sulfur flow battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that, The active material of the positive electrode is nickel hydroxide, the active material of the negative electrode is polysulfide containing S22- / S2- The separator is a cation exchange membrane, the electrolyte is an alkaline aqueous solution, and sodium hydroxide or potassium hydroxide is selected as the supporting electrolyte for the positive electrode and the negative electrode. containing S22- / S2- The polysulfide is sodium polysulfide or potassium polysulfide. The cation exchange membrane is a perfluorosulfonic acid membrane. The carrier of the active material of the positive electrode and the negative electrode is a nickel mesh. The current collector of the positive electrode and the negative electrode is flexible graphite.

2. The alkaline nickel sulfur flow battery of claim 1, wherein, The molar concentration of potassium ions or sodium ions in the electrolyte is 1-9 mol / L, the molar concentration of hydroxide ions is 1-6 mol / L, and the molar concentration of sulfur ions is 1-3 mol / L.

3. A method of making an alkaline nickel sulfur flow battery, characterized by, Preparation of the alkaline nickel-sulfur flow battery of claim 1, comprising: Mixing the powder containing nickel hydroxide, conductive agent of activated carbon and binder uniformly to form a slurry, and coating the slurry on the nickel mesh; Dissolving sodium hydroxide or potassium hydroxide in an aqueous solution to form an alkaline solution, and adding the alkaline solution to the positive electrode cavity; Dissolving sodium sulfide and sodium hydroxide or potassium hydroxide in an aqueous solution to form a sodium sulfide aqueous solution, and dissolving solid sulfur particles in the sodium sulfide aqueous solution to form a negative electrode electrolyte; Adding the negative electrode electrolyte and the pre-configured nickel mesh to the negative electrode cavity.

4. The method of producing a basic nickel-sulfur flow battery according to claim 3, characterized by, Further comprising: Pretreating the nickel mesh to form a nickel sulfide layer on the surface of the nickel mesh.

5. The method of producing a basic nickel-sulfur flow battery according to claim 4, characterized in that, The pretreatment of the nickel mesh to form a nickel sulfide layer on the surface of the nickel mesh comprises: Cleaning the nickel mesh in acetone and hydrochloric acid to remove surface oil stains and oxides; Washing the cleaned nickel mesh with clean water and drying; Boiling the dried nickel mesh in a potassium disulfide or sodium disulfide solution until the surface color changes from silver to black, forming a dense nanoflower-shaped nickel sulfide layer.

6. The method of producing a basic nickel-sulfur flow battery according to claim 5, wherein The molar concentration of the potassium disulfide is 1 mol / L, and the boiling time is 4-5 h.

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