Controllable electrochemical etching strategy based on solubility product difference: preparation method of barium sulfate modified NiCo-LDH aqueous alkaline zinc battery positive electrode material

Abstract

The invention relates to a controllable electrochemical etching strategy based on solubility product difference, in particular to a preparation method of a barium sulfate modified NiCo-LDH aqueous alkaline zinc battery positive electrode material, which comprises the following steps: firstly, dissolving 1, 4-phthalic acid and sodium hydroxide in a molar ratio of 1: 2 in water to obtain a solution A; dissolving barium nitrate pentahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate and ammonium fluoride in water according to a molar ratio of (0-1.5): 1: 4: 10 to obtain a solution B; the preparation method comprises the following steps: fully mixing the solutions, transferring the mixed solution into an autoclave containing foamed nickel (NF), and carrying out solvothermal reaction to obtain a tri-metal Co / Ni / Ba-MOF precursor (CNBx-BDC); cNBx-BDC is used as a working electrode, a platinum wire is used as a counter electrode, Hg / HgO is used as a reference electrode, 5-6M potassium hydroxide and 0.05-0.06 M sodium sulfate are used as electrolyte, a three-electrode system and a cyclic voltammetry method are adopted, electrochemical etching is carried out at the scanning rate of 20-30mV s <-1 > under the voltage range of 0-0.5 V, and the barium sulfate nanodot functionalized Co / Ni / Ba-LDH electrode (BS (at) CN-LDH) is obtained after six times of circulation. The unique porous structure can provide more electrochemical active sites and enhance electrolyte infiltration capacity, and the constructed heterostructure forms a strong built-in electric field, accelerates charge transfer, reduces ion diffusion energy barriers and improves energy utilization efficiency.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage materials, specifically a barium sulfate (BaSO4)-modified nickel-cobalt layered double hydroxide (NiCo-LDH) heterostructure material prepared by a controllable electrochemical etching strategy based on solubility product (Ksp) differences, and its application as a positive electrode material for high-performance aqueous alkaline zinc batteries (AZIBs). This material significantly improves charge transfer kinetics by creating strong built-in electric fields (BEFs). Background Art

[0002] Growing global energy demands, coupled with increasingly severe environmental challenges, necessitate the development of efficient and sustainable energy storage technologies. While lithium-ion batteries (LIBs) dominate portable electronic devices and electric vehicles, their resource sustainability, safety risks, and complex recycling processes limit their development and drive the exploration of alternative systems. Therefore, the design and development of high-performance electrochemical energy storage materials has become a major focus of scientific research.

[0003] Aqueous alkaline zinc batteries (AZIBs) are ideal candidates for large-scale energy storage systems due to their abundant zinc reserves, inherent non-flammability, low cost, and environmental friendliness. However, their cathode materials generally suffer from sluggish reaction kinetics, which limits the overall energy and power density of the battery. Among all cathode materials, layered double hydroxides (LDHs) are considered potential high-performance cathode materials due to their tunable interlayer structure and abundant surface active sites. However, their inherent low electrical conductivity and anisotropic ion transport properties severely restrict the charge transfer efficiency.

[0004] Existing technologies have been used to enhance electron mobility and ion desolvation kinetics by creating built-in electric fields (BEFs). However, conventional synthetic methods struggle to achieve atomic-level control of heterointerfaces, resulting in a limited electrochemically active surface and a difficult balance between charge transfer efficiency and structural stability. Furthermore, existing strategies (such as sulfide-LDH heterostructures) require multiple, long-term reactions and are prone to introducing impurities, which can compromise material stability.

[0005] An electrochemical etching strategy based on solubility product differential regulation exploits the significant differences in solubility between metal electrolytes to precisely anchor specific nanodot heterostructures, with process accuracy down to the micron level. Consequently, the construction of barium sulfate-modified NiCo-LDH and its derivative electrode materials presents a significant challenge in modern energy storage material technology and an opportunity to increase the power of energy storage devices. Summary of the Invention

[0006] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art. An electrochemical etching strategy based on Ksp difference is proposed. By precisely controlling the heterogeneous interface between BaSO4 and NiCo-LDH, the construction of strong BEFs is achieved, thereby breaking through the performance bottleneck of traditional LDHs materials.

[0007] The technical solution of the present invention is:

[0008] The present invention provides a controllable electrochemical etching strategy based on solubility product difference: a method for preparing a NiCo-LDH aqueous alkaline zinc battery positive electrode material modified with barium sulfate, comprising the following steps:

[0009] (1) 1,4-Benzenedicarboxylic acid and sodium hydroxide at a molar ratio of 1:2 were dissolved in water to obtain solution A. Then, barium nitrate pentahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and ammonium fluoride at a molar ratio of 0 to 1.5:1:4:10 were dissolved in water to obtain solution B. The above solutions were thoroughly mixed and transferred to an autoclave containing nickel foam (NF). The autoclave was heated at 140°C for 6 h to obtain a trimetallic Co / Ni / Ba-MOF precursor, named CNBx-BDC, where x ranged from 0 to 1.5.

[0010] The molar ratio of barium nitrate pentahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate and ammonium fluoride is (0-1.5):1:4:10, for example, it can be 0.32:1:4:10, 0.38:1:4:10, 0.5:1:4:10, 0.75:1:4:10, 1.3:1:4:10, 1.43:1:4:10 or 1.5:1:4:10, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0011] Preferably, the molar ratio of barium nitrate pentahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate and ammonium fluoride is 0.5:1:4:10.

[0012] (2) CNBx-BDC (x = 0-1.5) was used as the working electrode, platinum wire as the counter electrode, Hg / HgO as the reference electrode, 5-6 mol potassium hydroxide and 0.05-0.1 mol sodium sulfate as the electrolyte. A three-electrode system was used and cyclic voltammetry was performed in the voltage range of 0-0.5 V at a rate of 20-30 mV s -1 Electrochemical etching was performed at a scan rate of , and after 6 cycles, a barium sulfate nanodot functionalized Co / Ni / Ba-LDH electrode was obtained, named BS@CN-LDH.

[0013] The above x is 0 to 1.5, for example, it can be 0.3, 0.37, 0.43, 0.45, 0.5, 0.67, 0.73, 0.84, 1.0, 1.13, 1.27, 1.35, 1.43 or 1.5, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0014] Preferably, x is 1.0.

[0015] The above-mentioned potassium hydroxide molar mass is 5~6M, for example, can be 5M, 5.12M, 5.2M, 5.33M, 5.42M, 5.48M, 5.5M, 5.7M, 5.83M, 5.87M, 5.9M, 5.98M or 6M etc., but is not limited to the numerical value enumerated, and other numerical values ​​not enumerated within this scope are equally applicable.

[0016] Preferably, the potassium hydroxide molar mass is 6M.

[0017] The sodium sulfate molar mass is 0.05 to 0.1 M, for example, 0.05 M, 0.06 M, 0.063 M, 0.071 M, 0.086 M, 0.093 M or 0.1 M, but is not limited to the listed values. Other values ​​not listed within this range are also applicable.

[0018] Preferably, the molar mass of sodium sulfate is 0.05M.

[0019] The voltage range is 0.48 to 0.5 V, for example, it can be 0.48, 0.49 or 0.5, but is not limited to the listed values. Other values ​​not listed within the range are also applicable.

[0020] The above scan rate is 20-30 mV s -1 , for example, it can be 20.0mV s -1 , 21.2mV s -1 , 22mV s -1 , 23.5mV s -1 , 24.6mV s -1 , 25.0mV s -1 , 26.3mV s -1 , 27.8mV s -1 , 28.6mV s -1 , 29.7mV s -1 、30.0mV s -1 However, the present invention is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0021] Preferably, the scan rate is 25 mV s -1 .

[0022] The present invention uses potassium hydroxide and sodium sulfate as electrolytes, which, on the one hand, provide the basic structure of layered double hydroxide and important ions for etching using solubility product, and on the other hand, ensure that a large number of free ions are contained, thereby improving the specific capacitance and cycle efficiency of aqueous alkaline zinc batteries. At the same time, CNBx-BDC is used as the working electrode, platinum wire as the counter electrode, and Hg / HgO as the reference electrode. A three-electrode system is used for cyclic etching, and BaSO4 (Ksp = 1.1×10 -10 ) and CoSO4(Ksp≈3.6×10 -6 ) enables the preferential etching of Ba sites, anchoring BaSO4 nanodots (5-20nm in diameter) on the NiCo-LDH surface, ultimately forming the BS@CN-LDH heterostructure. Its porous structure provides a large number of electrochemically active sites, enhancing electrolyte penetration. The heterojunction interface forms strong BEFs, accelerating charge transfer and reducing the ion diffusion energy barrier.

[0023] Furthermore, in step (1), 1,4-benzenedicarboxylic acid and sodium hydroxide at a molar ratio of 1:2 are dissolved in water to obtain solution A, and then barium nitrate pentahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and ammonium fluoride at a molar ratio of 0 to 1.5:1:4:10 are dissolved in water to obtain solution B. The above solutions are thoroughly mixed and transferred to an autoclave containing nickel foam (NF), heated at 140°C for 6 hours to obtain a trimetallic Co / Ni / Ba-MOF precursor, named CNBx-BDC, where x is 0 to 1.5.

[0024] The purpose of ultrasonic dispersion in step (1) is to synthesize a trimetallic Co / Ni / Ba-MOFs (CNBx-BDC) precursor with uniform morphology and size.

[0025] Furthermore, the type and amount of water in step (1) should satisfy 35 mL of deionized water.

[0026] Furthermore, in step (2), CNBx-BDC is used as a working electrode, wherein x represents the relative content of Ba in the MOF precursor, and preferably, x is 1.

[0027] Furthermore, in step (2), 5-6M potassium hydroxide and 0.05-0.1M sodium sulfate are used as electrolytes, and deionized water is added to completely dissolve them.

[0028] Furthermore, in step (2), a three-electrode system is used for cyclic voltammetry electrochemical etching, the purpose of which is to precisely control the electrode potential, thereby precisely and selectively etching the target site area, and dynamically controlling the etching process, thereby achieving uniform and stable etching.

[0029] The present invention also provides a NiCo-LDH positive electrode material prepared by any of the preparation methods described above.

[0030] The present invention further provides an application of a NiCo-LDH cathode material prepared by any of the preparation methods described above. The NiCo-LDH cathode material can be applied to a high-performance aqueous alkaline zinc battery system.

[0031] Beneficial effects of the present invention:

[0032] The present invention provides a method for preparing a NiCo-LDH cathode material. A significant solubility product difference regulation strategy is adopted to construct a nanodot-modified LDH cathode material. Its porous structure can provide more electrochemically active sites, enhance electrolyte penetration, and form powerful BEFs, which accelerates charge transfer, reduces the ion diffusion energy barrier, and improves energy utilization efficiency.

[0033] The NiCo-LDH cathode material prepared by the present invention is used as an electrode cathode material in aqueous alkaline zinc batteries. The optimized barium sulfate-modified NiCo-LDH electrode material, under the same test conditions, assembled BS@CN-LDH / / rGO-Zn full battery achieved a high efficiency of 747.9Wh kg -1 High energy density (power density 0.27kW kg -1 ), surpassing most reported zinc-based energy storage devices. The material was electrochemically tested in a three-electrode system and showed a high conductivity at 2 mA cm -2 At this current density, the specific capacity of the BS@CN-LDH electrode reached 450.5 mAh g -1 (11352.8mF cm -2 ), and the capacity retention rate after 10,000 cycles was 83.3%. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] In order to further understand the present invention, the present invention will be further described with reference to the accompanying drawings and embodiments.

[0036] The experimental methods involved in the following examples are conventional methods unless otherwise specified. The instruments and reaction materials used are all commercially available unless otherwise specified.

[0037] Example 1

[0038] The present invention provides a method for preparing a NiCo-LDH cathode material, comprising the following steps:

[0039] (1) Synthesis of CoNiBa-MOF (CNBx-BDC) precursor:

[0040] First, 0.42 mmol of barium nitrate pentahydrate, 0.84 mmol of cobalt nitrate hexahydrate, 3.36 mmol of nickel nitrate hexahydrate, and 8.4 mmol of ammonium fluoride were dissolved in a solution of 1,4-benzenedicarboxylic acid (H2BDC) and sodium hydroxide in a molar ratio of 1:2. Ultrasonic dispersion was then performed for 20 minutes to thoroughly mix the mixture. The homogeneous solution was transferred to an autoclave containing a 1×5 cm piece of nickel foam (NF) and subjected to a hydrothermal reaction at 140°C for 6 hours. Finally, the nickel foam was removed, rinsed alternately with deionized water and ethanol, and dried in a vacuum oven at 60°C for 12 hours to obtain the trimetallic Co / Ni / Ba-MOFs (CNBx-BDC) precursor.

[0041] The preparation process of metal Co / Ni / Ba-MOF (CNBx-BDC) precursor can be found in Figure 1 Flowchart of the process.

[0042] For CNB-BDC's appearance, see Figure 2 and Figure 3 Scanning electron microscopy (SEM) images of the nanostructured carbon nanosheets showed that the nanostructured carbon nanosheets were uniformly distributed and smooth, with a thickness of ∼500 nm.

[0043] (2) Preparation of BS@CN-LDH material samples:

[0044] The CNBx-BDC obtained in step (1) was used as the working electrode, platinum wire as the counter electrode, Hg / HgO as the reference electrode, 6M potassium hydroxide and 0.05M sodium sulfate as the electrolyte, and a three-electrode system was used to perform cyclic voltammetry at a voltage range of 0 to 0.5 V at a rate of 25 mV s -1 After 6 cycles, the sample was washed with deionized water and dried at room temperature to obtain a barium sulfate nanodot functionalized Co / Ni / Ba-LDH electrode (BS@CN-LDH) material sample.

[0045] Transmission electron microscopy (TEM) images of BS@CN-LDH material samples are shown in Figure 4 The image shows that the porous accordion-like structure formed after etching provides a more precise etching site.

[0046] High-resolution transmission electron microscopy images of BS@CN-LDH material samples. Figure 5 As shown, the interface lattice at the distorted heterogeneous interface is shown in Figure 6 , and TEM mapping analysis was performed on it, the results are as follows Figure 7 As shown, the lattice matching and interface distortion of Ni(OH)2 and BaSO4 were verified.

[0047] The optimized atomic geometry model of this material can be found in Figure 8 .

[0048] The constant current charge and discharge curves (GCD) of this material at different current densities are shown in Figure 9 .

[0049] The capacity retention rate of this material after cycling can be found in Figure 10 .

[0050] The energy density of the full battery used for this material can be found in Figure 11 .

[0051] The NiCo-LDH cathode material prepared above was applied to the BS@CN-LDH / / rGO-Zn full battery. The experiment found that the barium sulfate modified NiCo-LDH cathode material has excellent electrochemical performance. The three-electrode system was used for testing. At 2 mA cm -2 Up to 16mAcm -2 The specific capacity and rate performance of BS@CN-LDH were tested at a current density of 450.5 mAh g -1 (2mAcm -2 ), with a capacity retention rate of 83.3% after 10,000 cycles, showing extremely strong cycle stability, and the full battery energy density reached 747.9Wh kg -1 .

[0052] Example 2

[0053] The difference between this embodiment and embodiment 1 is that the Ba content in step (1) is optimized: the amount of barium nitrate pentahydrate in solution B is replaced by 0.21 mmol and 0.63 mmol, respectively, to obtain B 0.5 S@CN-LDH,B 1.5 S@CN-LDH, other conditions were the same.

[0054] The final B 0.5 S@CN-LDH and B 1.5 The constant current charge and discharge curves (GCD) of S@CN-LDH cathode materials at different current densities are shown as follows: Figure 12 , Figure 13 shown.

[0055] Example 3

[0056] The difference between this embodiment and embodiment 1 is that Ba is replaced by Al, Cr, etc. to prepare CNM-LDH (M=Al, Cr, etc.), and other conditions are the same.

[0057] The capacitance performance comparison of CNM-LDH obtained by replacing metals such as Al and Cr can be found in Figure 14 , Figure 15 .

[0058] Example 4

[0059] The obtained barium sulfate modified NiCo-LDH cathode material was theoretically calculated and analyzed.

[0060] UPS spectra of barium sulfate and CN-LDH can be found in Figure 16 , it was calculated that the work functions of BaSO4 and CN-LDH are 4.57eV and 3.87eV respectively, and the work function difference ΔΦ=0.70eV.

[0061] The band structure model, charge density difference diagram and density of states (DOS) analysis of barium sulfate and CN-LDH are respectively shown in Figure 17 , Figure 18 and Figure 19 . BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 Flow chart of the preparation of the Co / Ni / Ba-MOFs (CNBx-BDC) precursor obtained in Example 1;

[0063] Figure 2 is a scanning electron microscope image (SEM) of the CNB-BDC obtained in Example 1;

[0064] Figure 3 is a scanning electron microscope image (SEM) of the CNB-BDC obtained in Example 1;

[0065] Figure 4 TEM image of BS@CN-LDH obtained in Example 1;

[0066] Figure 5 This is a high-resolution transmission electron microscopy image of BS@CN-LDH obtained in Example 1;

[0067] Figure 6 The interface lattice diagram at the distorted heterogeneous interface of BS@CN-LDH obtained in Example 1;

[0068] Figure 7 TEM mapping of BS@CN-LDH obtained in Example 1;

[0069] Figure 8 This is the optimized atomic geometry model diagram of BS@CN-LDH obtained in Example 1;

[0070] Figure 9 The constant current charge-discharge curve (GCD) of BS@CN-LDH obtained in Example 1 at different current densities;

[0071] Figure 10 This is the long-cycle stability diagram of BS@CN-LDH obtained in Example 1;

[0072] Figure 11 This is the full-cell energy density diagram of the BS@CN-LDH obtained in Example 1;

[0073] Figure 12 B obtained in Example 2 0.5 Galvanostatic charge-discharge curves (GCD) of S@CN-LDH at different current densities;

[0074] Figure 13 B obtained in Example 2 1.5 Galvanostatic charge-discharge curves (GCD) of S@CN-LDH at different current densities;

[0075] Figure 14 The constant current charge-discharge curves (GCD) of CNM-LDH obtained by replacing Ba with Al in Example 3 at different current densities;

[0076] Figure 15 The constant current charge-discharge curves (GCD) of CNM-LDH obtained by replacing Ba with Cr in Example 3 at different current densities;

[0077] Figure 16 UPS spectra of barium sulfate and CN-LDH obtained in Example 4;

[0078] Figure 17 : This is a model diagram of the energy band structure of barium sulfate and CN-LDH obtained in Example 4;

[0079] Figure 18 : is the charge density difference diagram of barium sulfate and CN-LDH obtained in Example 4;

[0080] Figure 19 This is the density of states (DOS) analysis diagram of barium sulfate and CN-LDH obtained in Example 4.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, and modifications made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A controllable electrochemical etching strategy based on solubility product difference: a method for preparing a NiCo-LDH aqueous alkaline zinc battery cathode material modified with barium sulfate, characterized in that: The following steps are involved: (1) 1,4-Benzenedicarboxylic acid and sodium hydroxide at a molar ratio of 1:2 were dissolved in water to obtain solution A, and then barium nitrate pentahydrate, cobalt nitrate hexahydrate, nickel nitrate hexahydrate, and ammonium fluoride at a molar ratio of 0-1.5:1:4:10 were dissolved in water to obtain solution B. After the above solutions were fully mixed, they were transferred to an autoclave containing nickel foam (NF) and heated at 140°C for 6 hours to obtain a trimetallic Co / Ni / Ba-MOF precursor named CNBx-BDC. x ranges from 0 to 1.

5. (2) CNBx-BDC was used as the working electrode, platinum wire as the counter electrode, Hg / HgO as the reference electrode, 5-6 mol potassium hydroxide and 0.05-0.1 mol sodium sulfate as the electrolyte. A three-electrode system was used and cyclic voltammetry was used. The voltage range was 0-0.5 V and the reaction temperature was 20-30 mV s -1 Electrochemical etching was performed at a scan rate of , and after 6 cycles, a barium sulfate nanodot functionalized Co / Ni / Ba-LDH electrode was obtained, named BS@CN-LDH.

2. The preparation method according to claim 1, characterized in that The CNBx-BDC prepared in step (1) exhibits a nanosheet structure, and the Co, Ni, and Ba elements are evenly distributed and grown in the form of a nanoarray on the nickel foam current collector.

3. The preparation method according to claim 1, characterized in that The BS@CN-LDH electrode prepared in step (2) maintains the nanosheet structure of the matrix, and accordion-shaped cracks appear at the edge to promote rapid mass transfer; the in-situ formed BaSO4 nanodots are anchored in the NiCo-LDH phase to form a heterostructure with a strong built-in electric field.

4. A controllable electrochemical etching strategy based on solubility product difference: a method for preparing a NiCo-LDH aqueous alkaline zinc battery cathode material modified with barium sulfate, characterized in that: BS@CN-LDH can be used as the cathode for aqueous alkaline zinc batteries with a specific capacity of ≥450 mAh g -1 (2mA cm - 2), after 10,000 cycles, the capacity retention rate is ≥83.3%, at 0.27kW kg -1 The energy density can reach 747.9Wh kg at a power density of -1 .

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