Aqueous cadmium ion-vanadium dioxide battery and preparation method and application thereof

Abstract

The application provides a water-based cadmium ion-vanadium dioxide battery and a preparation method and application thereof, and relates to the field of marine energy storage.The application comprises a negative electrode, a positive electrode, a diaphragm and a water-based electrolyte; the negative electrode is metal cadmium or a cadmium-based alloy; the active substance of the positive electrode is metastable monoclinic phase vanadium dioxide; the diaphragm is a glass fiber diaphragm; the water-based electrolyte is an aqueous solution containing cadmium salt; and the total concentration of the cadmium salt in the water-based electrolyte is 1-4 mol / L.The water-based vanadium dioxide-cadmium metal secondary battery has the advantages of a safe water-based electrolyte system, high rate performance and super-long cycle life, and has significant advantages in marine energy storage.

Description

Technical Field

[0001] This invention relates to the field of marine energy storage, and in particular to an aqueous vanadium dioxide-cadmium metal secondary battery. Background Technology

[0002] With the large-scale utilization of renewable energy and the rapid development of the electric vehicle industry, higher demands are being placed on the safety, cost, cycle life, and environmental friendliness of large-scale energy storage systems and power batteries. While traditional lithium-ion batteries have high energy density, their safety and economic viability in large-scale energy storage and specific application scenarios are challenged due to the flammability and explosion risks of organic electrolytes, expensive raw material costs, and complex production environment control. Against this backdrop, aqueous secondary batteries, due to their use of non-flammable aqueous electrolytes, possess significant advantages such as intrinsic safety, low cost, environmental friendliness, high ionic conductivity, and simple manufacturing processes, making them a key research direction for next-generation energy storage technology. The ocean contains abundant wind, solar, and tidal energy resources, but these offshore power platforms exhibit strong intermittency and volatility, urgently requiring large-scale energy storage systems for smoothing and peak regulation. Offshore energy storage systems place high demands on battery safety and cycle life; the explosion risk of traditional lithium batteries cannot meet these safety requirements, thus necessitating a focus on safer aqueous batteries. Currently, research on aqueous battery systems mainly focuses on those based on multivalent ions (such as Zn). 2+ Mg 2+ Al 3+ Novel electrochemical systems for charge carriers are being developed, with aqueous zinc-ion batteries showing the most rapid growth.

[0003] In cathode materials, vanadium-based oxides (such as V₂O₅, VO₂, etc.) provide ample space for ion insertion / extraction due to their layered or tunnel-like crystal structures, and vanadium exhibits a wide range of valence states (V₂O₅, VO₂, etc.). 2+ To V 5+ Vanadium dioxide (VO2), with its high theoretical capacity, is considered a highly promising cathode material for aqueous batteries. In particular, vanadium dioxide exhibits excellent ion transport properties due to its unique metal-insulator phase transition characteristics and crystal structure that facilitates rapid ion transport (such as Li). + Zn 2+ H + Storage potential. However, in aqueous electrolytes, VO2 still faces some key challenges as a cathode material: First, during cycling, especially with protons (H+)... +In acidic electrolytes where violent interactions occur, the crystal structure of VO2 may undergo irreversible dissolution or collapse, leading to rapid capacity decay. Secondly, its electronic conductivity needs to be further improved to support high-rate charging and discharging. Thirdly, how to design an efficient and stable negative electrode that matches VO2 to construct a complete and high-performance aqueous battery system is a current research challenge.

[0004] In terms of anode materials, zinc is currently the most widely studied anode, but it suffers from problems such as dendrite growth, hydrogen evolution reaction, and surface passivation, affecting cycle stability and coulombic efficiency. Cadmium (Cd), as a mature anode material, has been widely used in nickel-cadmium batteries. It possesses advantages such as high hydrogen evolution overpotential, relatively stable surface layer in aqueous electrolytes, good electrochemical reversibility, and long cycle life. However, traditional nickel-cadmium batteries use alkaline electrolytes and nickel hydroxide cathodes, resulting in memory effect and low energy density. Currently, there are few reports on combining cadmium anodes with novel high-performance cathode materials (such as VO2) to construct novel aqueous battery systems. Summary of the Invention

[0005] In view of this, the present invention proposes an aqueous cadmium-ion-vanadium dioxide battery, its preparation method and application.

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

[0007] An aqueous cadmium-ion battery includes a negative electrode, a positive electrode, a separator, and an aqueous electrolyte;

[0008] The negative electrode is metallic cadmium or a cadmium-based alloy;

[0009] The active material of the positive electrode is metastable monoclinic vanadium dioxide (VO2(B)).

[0010] The diaphragm is a glass fiber diaphragm (GF / D).

[0011] The aqueous electrolyte is an aqueous solution containing cadmium salt; preferably, the cadmium salt is selected from one or more of cadmium sulfate, cadmium acetate, and cadmium perchlorate.

[0012] Further, the total concentration of cadmium salts in the aqueous electrolyte is 1M to 4M. More preferably, the aqueous electrolyte is a mixed solution of cadmium sulfate and cadmium acetate, wherein the concentration of cadmium sulfate is 1M to 3M and the concentration of cadmium acetate is 0.5M to 1M. Most preferably, the aqueous electrolyte is a mixed solution of 3M cadmium sulfate and 1M cadmium acetate.

[0013] Further, the preparation method of the metastable monoclinic vanadium dioxide includes the following steps: dispersing vanadium dioxide powder in water, adding ethylene glycol, stirring to obtain a suspension, hydrothermally reacting the suspension at 175-185 ℃ for 14-16 h, then naturally cooling to room temperature, filtering, washing, and drying the obtained product to obtain metastable monoclinic vanadium dioxide; the mass-volume ratio of vanadium dioxide powder, water, and ethylene glycol is (440-460) mg: (18-22) mL: (9-11) mL.

[0014] Furthermore, during the first charge cycle of the aqueous cadmium-ion battery, the metastable monoclinic vanadium dioxide cathode undergoes an amorphous structure transformation, and some vanadium elements are oxidized from +4 to +5 valence. This process results in a significant increase in the cathode specific capacity relative to the initial crystalline VO2(B).

[0015] The present invention also provides a method for preparing the aqueous cadmium-ion battery, comprising the following steps:

[0016] (1) Preparation of positive electrode: Metastable monoclinic vanadium dioxide (VO2(B)) powder, Ketjen black and PTFE binder are mixed in proportion, and isopropanol solvent is added for grinding. After rolling and drying, positive electrode sheet is made.

[0017] (2) Negative electrode preparation: using cadmium sheet or cadmium foil as the negative electrode, or using cadmium powder to prepare the negative electrode sheet;

[0018] (3) Electrolyte preparation: Dissolve one or more selected cadmium salts in deionized water to prepare an aqueous electrolyte of the required concentration;

[0019] (4) Battery assembly: The positive electrode, separator and negative electrode are placed into the battery case in sequence, electrolyte is injected and sealed to obtain an aqueous cadmium-ion battery.

[0020] Further, in step (1), the mass ratio of metastable monoclinic vanadium dioxide powder, Ketjen black and PTFE binder is (65-75):(15-25):(8-12).

[0021] Furthermore, in step (1), the ratio of the total mass of metastable monoclinic vanadium dioxide powder, Ketjen black and PTFE binder to the volume of isopropanol in kg / L is (0.02-0.05):1.

[0022] This invention relates to the application of an aqueous cadmium-ion vanadium dioxide battery in marine energy storage.

[0023] Furthermore, the operating voltage range of the aqueous cadmium-ion-vanadium dioxide battery of the present invention is 0.2-1.5V and 0-1.5V.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. High specific capacity: This invention is the first to discover and utilize metastable VO2(B) as the positive electrode of cadmium-ion battery. During the first charge cycle, a unique amorphous state transformation and vanadium valence state increase (part of the +4 valence vanadium increases to +5 valence) synergistic effect occur, which leads to a breakthrough improvement in the specific capacity of aqueous cadmium metal battery.

[0026] 2. Excellent electrolyte system: Through screening and optimization, it was found that the mixed electrolyte of cadmium sulfate and cadmium acetate, especially the system of 3M cadmium sulfate + 1M cadmium acetate, can most effectively promote the above-mentioned electrochemical activation process and achieve the best ionic conductivity and interfacial stability, thus exhibiting the best comprehensive electrochemical performance.

[0027] 3. High safety and low cost: The whole battery uses an aqueous electrolyte, which completely avoids the risk of combustion and explosion of organic electrolytes. In addition, the raw materials used are low cost and the preparation process is simple.

[0028] 4. Providing a new direction for cadmium-based batteries: This invention has found a high-performance positive electrode matching material for cadmium metal negative electrodes, providing a new technical path for the development of new safe and low-cost aqueous secondary batteries.

[0029] 5. Advantages of marine energy storage applications: The aqueous vanadium dioxide-cadmium metal secondary battery of this invention, with its inherently safe aqueous electrolyte system, high rate performance, and ultra-long cycle life, is highly compatible with the needs of marine energy storage scenarios and has the following significant advantages:

[0030] (1) Grid connection adaptation of new energy at sea: The battery is inherently non-flammable, eliminating the risk of thermal runaway of organic electrolyte in the high temperature and humidity environment at sea; the high rate performance can quickly respond to the power fluctuations of offshore wind power and photovoltaic; the ultra-long cycle life significantly reduces the operation and maintenance costs of unattended offshore scenarios.

[0031] (2) Potential for power supply of deep-sea equipment: The cadmium metal anode has a high hydrogen evolution overpotential and good surface stability. The VO2(B) amorphous structure is flexible and can buffer volume changes under high pressure in the deep sea. Its excellent cycle stability and coulombic efficiency (99.75%) are suitable for long-term maintenance-free power supply scenarios such as seabed observation network and deep-sea buoy.

[0032] (3) Marine microgrids and island and reef applications: The whole water system is environmentally friendly and has strong adaptability to a wide temperature range. It can support the energy self-sufficiency of marine ranches and island and reef independent microgrids in the "wind-solar-storage-use" system, and provide stable power for automatic feeding, water quality monitoring, communication equipment, etc. Attached Figure Description

[0033] Figure 1This is a comparison image of the XRD pattern of metastable monoclinic vanadium dioxide VO2(B) prepared in Example 1 with that of a standard PDF card. In the image, 2θ refers to the diffraction angle.

[0034] Figure 2 This is a SEM image of the metastable monoclinic vanadium dioxide VO2(B) prepared in Example 1;

[0035] Figure 3 This is a comparison chart of the cycle performance of aqueous cadmium metal batteries assembled with the five electrolytes configured in Example 2 at a working voltage of 0.2-1.5V;

[0036] Figure 4 This is the XRD pattern of the vanadium dioxide cathode sheet after one cycle in Example 3;

[0037] Figure 5 This is a SEM image of the vanadium dioxide cathode sheet after one cycle in Example 3;

[0038] Figure 6 The image shows the CV (cyclic voltammetry) image of the vanadium dioxide-cadmium battery measured in Example 4 at 0-1.5V.

[0039] Figure 7 These are multi-scan rate CV (cyclic voltammetry) images of the vanadium dioxide-cadmium battery in Example 4 at 0.1-10 mV / s;

[0040] Figure 8 This is the charge-discharge curve of the vanadium dioxide-cadmium battery measured in Example 4 at 1 A / g;

[0041] Figure 9 This is a graph showing the rate performance of the vanadium dioxide-cadmium battery measured in Example 4 at an operating voltage of 0-1.5V.

[0042] Figure 10 This is a graph showing the long-cycle performance of the vanadium dioxide-cadmium battery at a working voltage of 0-1.5V, as measured in Example 4. Detailed Implementation

[0043] Unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods;

[0044] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0045] The Chinese meanings of some of the abbreviations in this invention are as follows:

[0046] PTFE: Polytetrafluoroethylene.

[0047] Example 1

[0048] The VO2(B) used in this invention is synthesized using a simple one-step hydrothermal method. 450 mg of V2O5 powder is dispersed in 20 mL of deionized water, and then 10 mL of ethylene glycol is added. The mixture is stirred for 1 h to obtain a suspension. The suspension is poured into a 50 mL polytetrafluoroethylene liner and hydrothermally reacted at 180 °C for 15 h. After naturally cooling to room temperature, the obtained product is filtered and washed three times with deionized water and anhydrous ethanol, respectively. After drying in air at 60 °C for 12 h, a dark blue product is obtained, which is the metastable monoclinic vanadium dioxide powder.

[0049] like Figure 1 As shown, the characteristic peaks of the synthesized VO2(B) are consistent with the reported standard values ​​(PDF card number: 31-1438, a = 12.030 Å, b = 3.693 Å, c = 6.420 Å), proving the successful synthesis of the desired VO2(B). Figure 2 The SEM images show that the synthesized VO2(B) is a nanorod structure.

[0050] Example 2

[0051] The positive electrode sheet was fabricated using the VO2(B) material obtained in Example 1 above, and a coin-type cadmium-ion battery was assembled, as detailed below:

[0052] Metastable monoclinic vanadium dioxide (VO2(B)) prepared in Example 1 was used as the positive electrode active material for an aqueous cadmium-ion battery. Ketjen black was used as a conductive agent, and polytetrafluoroethylene (PTFE) was used as a binder. The mass ratio of active material, conductive agent, and binder was 7:2:1. After mixing them in this ratio, isopropanol was added and the mixture was ground. The total mass ratio of metastable monoclinic vanadium dioxide, Ketjen black, and PTFE binder to the volume of isopropanol was 0.04:1 (kg / L). The electrode sheets were prepared by rolling and drying at 60 degrees Celsius for 10 hours. The electrode sheets were fabricated by stamping them into 10 mm diameter discs. The active material mass loading of the stamped electrode sheets was 3-4 mg / cm². CR2032 coin cells were used for assembly. Cadmium metal sheets and glass fiber (GF / D) were used as the counter electrode and separator, respectively. The electrolyte was cadmium salt dissolved in deionized water. Five electrolyte solutions were prepared as follows:

[0053] 1.1M cadmium sulfate aqueous solution;

[0054] 2.1M cadmium acetate aqueous solution;

[0055] 3.1M cadmium perchlorate aqueous solution;

[0056] 4.3M cadmium sulfate aqueous solution;

[0057] A 5.3M cadmium sulfate and 1M cadmium acetate mixed aqueous solution.

[0058] Aqueous vanadium dioxide-cadmium metal batteries were assembled using the five electrolytes mentioned above. At room temperature, the batteries were tested using a blue electrode testing system within a voltage range of 0.2-1.5V and a g / L capacity of 5A. -1 Charge-discharge tests were conducted under high current. The results are as follows: Figure 3 As shown, the mixed electrolyte of 3M cadmium sulfate and 1M cadmium acetate exhibits significant advantages, possessing the highest specific capacity and retaining 237.1 mAh g⁻¹ after 2000 cycles. -1 The specific capacity was high, with a capacity retention rate as high as 83.2% and an average coulombic efficiency of 99.75%. Studies have shown that when the cadmium sulfate concentration reaches 3M, Cd... 2+ The solvation structure undergoes a fundamental change, transforming from a hydrated ion into a complex ion [Cd(H₂O)₆(SO₄)₃] coordinated by both water and sulfate. 4- This structure significantly reduces Cd. 2+ The activity and quantity of surrounding free water molecules significantly inhibit hydrogen evolution side reactions and cadmium anode corrosion that lead to battery failure. Acetate ions may serve as an effective interface modifier. They can preferentially adsorb onto the cadmium electrode surface, guiding cadmium ions to deposit more uniformly through steric hindrance or electrostatic repulsion, thereby inhibiting dendrite growth and forming a more stable solid electrolyte interphase (SEI) film. Combining these two aspects, this mixed electrolyte simultaneously optimizes both the bulk phase and the interface. During desolvation and deposition processes, Cd... 2+ The smoother transport and reaction facilitate the formation of a dense, flat cadmium metal deposition layer, further improving electrochemical reversibility and cycle stability. Therefore, subsequent examples all used a mixed electrolyte of 3M cadmium sulfate and 1M cadmium acetate.

[0059] Example 3

[0060] For the aqueous cadmium-ion battery assembled in Example 2, after the first charge-discharge cycle, the battery was disassembled, and the vanadium dioxide positive electrode was removed. XRD and SEM tests were performed on the electrode after charge-discharge to observe its structural transformation. Compared to the initial XRD and SEM images of vanadium dioxide, after one charge-discharge cycle, VO2 underwent an amorphous transformation, completely changing from the original nanorod structure to an amorphous state. This was reflected in the XRD image where the characteristic peaks completely disappeared, exhibiting typical amorphous characteristics. The SEM image also showed the transformation of the nanorod structure into an amorphous structure. Figure 4 , Figure 5 As shown.

[0061] The core molecular structure of VO2(B) is a layered framework with an open tunnel structure, formed by irregular [VO6] octahedra connected by shared edges and corners. Amorphization completely reconstructs its cadmium storage space and pathways. In the amorphous state, the long-range order of the [VO6] octahedra is destroyed, but the short-range structural units still exist. This disordered network forms an isotropic, three-dimensionally connected continuous space. Cadmium ions are no longer confined to specific tunnels, but can more freely seek suitable energy sites for storage throughout the material, with the number of available active sites far exceeding the limitations of the crystal framework. During amorphization, a large number of dangling bonds, coordination defects, and structural distortions are generated, and these defects are precisely the highly active cadmium storage sites. The disordered network structure of amorphous vanadium dioxide has better flexibility and elasticity, and more uniformly buffers volume changes, thereby maintaining structural integrity. This directly translates into better cycling stability, enabling its high capacity to be maintained for longer periods.

[0062] Example 4

[0063] The aqueous vanadium dioxide-cadmium metal battery (electrolyte of 3M cadmium sulfate and 1M cadmium acetate) assembled in Example 2 was subjected to cyclic voltammetry (CV) testing, rate performance testing, and long-cycle performance testing. Figure 6 As shown, the cyclic voltammetry results also reveal that the electrochemical behavior of this vanadium dioxide-cadmium battery during the first charge-discharge cycle is drastically different from that in subsequent cycles, further confirming that an irreversible change occurred during the first charge-discharge cycle, while exhibiting relatively stable electrochemical behavior in subsequent cycles. The charge-discharge curves of the vanadium dioxide-cadmium metal battery at a current density of 1 A / g are shown below. Figure 8 As shown, after an irreversible change in the first cycle, the subsequent cycles are relatively stable, and the charge-discharge curves do not have obvious plateaus. Figure 6 In the CV images, the redox peaks are not significant in subsequent cycles, and in the low potential region (approximately 0-0.3 V), the curve begins to exhibit a certain degree of "bulging" or "rectangular" characteristics, indicating the presence of a surface-controlled rapid Faraday process (i.e., pseudocapacitive behavior) in this region. Furthermore, the two main peaks are relatively broad, rather than extremely narrow sharp peaks, suggesting that the reaction process may involve a mixture of surface-controlled (pseudocapacitive) and diffusion-controlled (cell-type) kinetic mechanisms. This is a common phenomenon in many electrode materials with open structures (such as VO2(B) tunnel structures), i.e., a hybrid energy storage mechanism. Figure 7 According to the results of multi-scan rate CV, the energy storage mechanism of this vanadium dioxide electrode is mainly a diffusion-controlled battery-type reaction. However, as the scan rate increases, the contribution of pseudocapacitance increases significantly, which is a typical hybrid energy storage mechanism.

[0064] like Figure 9As shown, this vanadium dioxide-cadmium metal battery exhibits excellent rate performance, with a specific capacity as high as 461.2 mAh / g at 0.5 A / g. Even when the current increases to 40 A / g, it still retains a capacity of 160.1 mAh / g. Furthermore, when the current returns from 40 A / g to 0.5 A / g, the specific capacity also returns to its normal level at 0.5 A / g and maintains stable cycling. This is due to the surface-controlled pseudocapacitive behavior providing a rapid current response. This allows the battery to retain a considerable portion of its capacity even when operating at high currents, achieving high power output and rapid charge / discharge. Figure 10 As shown, the battery achieves ultra-high specific capacity within a 0-1.5V operating window, with a second discharge specific capacity of up to 370.8 mAh / g and a specific capacity of 296.1 mAh / g after 3000 cycles, exhibiting a capacity retention rate of up to 79.85%.

[0065] 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 scope of the present invention should be included within the protection scope of the present invention.

Claims

1. An aqueous cadmium-ion-vanadium dioxide battery, characterized in that, The device includes a negative electrode, a positive electrode, a separator, and an aqueous electrolyte; the negative electrode is metallic cadmium or a cadmium-based alloy; the active material of the positive electrode is metastable monoclinic vanadium dioxide; the separator is a glass fiber separator; the aqueous electrolyte is an aqueous solution containing cadmium salts; the total concentration of cadmium salts in the aqueous electrolyte is 1-4 mol / L. The aqueous electrolyte is a mixed solution of cadmium sulfate and cadmium acetate, wherein the concentration of cadmium sulfate is 1-3 mol / L and the concentration of cadmium acetate is 0.5-1 mol / L. The preparation method of the metastable monoclinic vanadium dioxide includes the following steps: dispersing vanadium dioxide powder in water, adding ethylene glycol, stirring to obtain a suspension, hydrothermally reacting the suspension at 175-185 ℃ for 14-16 h, then naturally cooling to room temperature, filtering, washing, and drying the obtained product to obtain metastable monoclinic vanadium dioxide; the mass-volume ratio of vanadium dioxide powder, water, and ethylene glycol is (440-460) mg: (18-22) mL: (9-11) mL.

2. The aqueous cadmium-ion-vanadium dioxide battery according to claim 1, characterized in that, The aqueous electrolyte is a mixed solution of 3 mol / L cadmium sulfate and 1 mol / L cadmium acetate.

3. The method for preparing the aqueous cadmium-ion-vanadium dioxide battery according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Preparation of positive electrode: Metastable monoclinic vanadium dioxide, Ketjen black and polytetrafluoroethylene are mixed, and isopropanol solvent is added for grinding. After rolling and drying, positive electrode sheets are made. (2) Negative electrode preparation: using cadmium sheet or cadmium foil as the negative electrode, or using cadmium powder to prepare the negative electrode sheet; (3) Electrolyte preparation: Dissolve cadmium salt in deionized water to prepare an aqueous electrolyte; (4) Battery assembly: The positive electrode, separator and negative electrode are placed into the battery case in sequence, electrolyte is injected and sealed to obtain an aqueous cadmium-ion battery.

4. The preparation method of the aqueous cadmium-ion-vanadium dioxide battery according to claim 3, characterized in that, In step (1), the mass ratio of the metastable monoclinic vanadium dioxide, Ketjen black and polytetrafluoroethylene is (65-75):(15-25):(8-12).

5. The method for preparing an aqueous cadmium-ion-vanadium dioxide battery according to claim 3 or 4, characterized in that, In step (1), the ratio of the total mass of the metastable monoclinic vanadium dioxide, Ketjen black and polytetrafluoroethylene to the volume of isopropanol is (0.02-0.05):

1.

6. The aqueous cadmium-ion-vanadium dioxide battery obtained by the preparation method of the aqueous cadmium-ion-vanadium dioxide battery according to any one of claims 1-2 or any one of claims 3-5 is used in marine energy storage.

7. The application according to claim 6, characterized in that, The operating voltage range of the aqueous cadmium-ion-vanadium dioxide battery is 0-1.5V.

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