Preparation method of cobalt-nickel-mof-derived high-capacity phosphate cathode material and aqueous zinc-based alkaline battery

Abstract

The application discloses a preparation method of a cobalt-nickel MOF derived high-capacity phosphate positive electrode material and an aqueous zinc-based alkaline battery. The positive electrode material is prepared through a two-step hydrothermal process. In the first step, cobalt-nickel MOF is prepared. In the second step, the cobalt-nickel MOF is used as a precursor to perform hydrothermal phosphate treatment, so that the positive electrode material with high surface capacity is obtained and applied to the zinc-based alkaline battery. The electrode material preparation process is simple, the electrode material is applied to the positive electrode of the zinc-based alkaline battery, the electrode surface capacity is very high, and the electrode material has excellent application prospect.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-based alkaline battery technology, specifically relating to a high areal capacity phosphate cathode material derived from cobalt-nickel MOF. Background Technology

[0002] The diverse demands of the energy market for energy storage systems have spurred the development of various battery technologies. Zinc-based alkaline batteries, as one of many battery technologies, offer advantages such as low cost, environmental friendliness, and safety and reliability, making them suitable for various practical applications, such as large-scale grid storage. Commercially available zinc-based alkaline batteries are primarily primary batteries, such as zinc-nickel batteries, zinc-manganese batteries, zinc-silver batteries, and zinc-air batteries. However, with the rapid development of the electrical age, primary battery technology can no longer meet current practical needs, making the development of rechargeable secondary zinc-based alkaline batteries an inevitable trend.

[0003] Zinc-based alkaline battery systems mainly consist of a positive electrode material, a zinc negative electrode, and a specific electrolyte (a potassium hydroxide solution of a certain concentration). Zn(OH)₄ 2- / Zn (-1.26V vs. SHE) has a low redox potential and a high theoretical capacity (820mAh g). -1 Or 5855mAh cm -3 The relatively low market price of zinc resources and the simple and easy-to-operate production process make zinc-based alkaline batteries highly promising. Therefore, finding high-capacity cathode materials to match with zinc anodes and assembling battery systems with higher energy density has become an important breakthrough direction in the field of aqueous zinc-based alkaline batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a high-area-capacity phosphate cathode material derived from cobalt-nickel MOF and its preparation method, and to apply it to the field of aqueous zinc-based alkaline batteries. The cathode material is prepared using a two-step hydrothermal process, employing a hydrothermal cobalt-nickel MOF as a template, followed by a hydrothermal phosphate conversion process. The preparation process is simple and has excellent application prospects.

[0005] The cobalt-nickel MOF-derived ultra-high capacity phosphate cathode material described in this invention is cobalt-nickel phosphate derived from cobalt-nickel MOF. This phosphorylation process realizes the transformation of MOF into phosphate on the one hand, and on the other hand, it coats the outside of the MOF structure with a layer of self-grown cobalt-nickel phosphate.

[0006] The aqueous zinc-based alkaline battery of this invention comprises a positive electrode material, a negative electrode material, and an electrolyte. The positive electrode material is a cobalt-nickel MOF-derived ultra-high capacity phosphate positive electrode material, the negative electrode material is a commercially available zinc sheet, and the electrolyte comprises a certain concentration of potassium hydroxide and a saturated aqueous solution of soluble zinc salt.

[0007] The preparation method of high areal capacity phosphate cathode material derived from cobalt-nickel MOF includes the following steps:

[0008] Step 1: Preparation of Cobalt-Nickel MOFs

[0009] Step 1: Dissolve nickel salt, cobalt salt and organic ligand in a mixed solution composed of N,N-dimethylacetamide, anhydrous ethanol and deionized water. After stirring evenly, add to a three-dimensional substrate for hydrothermal reaction, wash and dry to obtain NiCo-MOF precursor.

[0010] Step 2: Dissolve cobalt salt, nickel salt, phosphate and urea in water. After the solution is stirred evenly, add NiCo-MOF precursor, carry out hydrothermal reaction, wash and dry to obtain cobalt-nickel MOF-derived phosphate electrode material.

[0011] The cobalt salt includes any one of cobalt nitrate, cobalt chloride, cobalt sulfate, or cobalt acetate; the nickel salt includes any one of nickel nitrate, nickel chloride, nickel sulfate, or nickel acetate; the phosphate salt includes any one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, or disodium hydrogen phosphate; and the organic ligand is terephthalic acid.

[0012] In step one, the molar ratio of nickel salt, cobalt salt, and organic ligand is 0.5–5.6:0.5–5.6:1–4;

[0013] The volume ratio of N,N-dimethylacetamide, anhydrous ethanol, and deionized water is 8-10:1-4:0.1-1.

[0014] In step one, the hydrothermal reaction temperature is 100℃~180℃, and the hydrothermal reaction time is 6h~24h. During the preparation of the cathode material according to this invention, the solution volume is 50%~90% of the volume of the high-pressure reactor.

[0015] The three-dimensional substrate includes hydrophilic carbon paper, nickel foam, titanium alloy mesh, or stainless steel mesh.

[0016] In step two, the molar ratio of cobalt salt, nickel salt, phosphate, and urea is 0.1–0.9: 0.1–0.9: 0.5–2.4: 0.01–0.05; the urea concentration in the solution is 0.001–1 M.

[0017] In step two, the hydrothermal reaction temperature is 100℃~200℃, and the hydrothermal reaction time is 1~36h. The solution volume during the preparation of the cathode material according to this invention is 50%~90% of the volume of the high-pressure reactor.

[0018] An aqueous zinc-based alkaline battery, comprising three parts: a phosphate positive electrode material, a zinc negative electrode material, and an electrolyte.

[0019] The electrolyte is a solution of potassium hydroxide and a saturated soluble zinc salt, wherein the concentration of potassium hydroxide is 0.1-10M, and the soluble zinc salt solution includes any one of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate, or zinc oxide.

[0020] The cathode material can also be a cobalt-nickel MOF, a cobalt MOF, or a nickel MOF.

[0021] The negative electrode material described in this invention is zinc sheet, zinc foil, or zinc powder.

[0022] The electrolyte of this invention comprises potassium hydroxide and saturated soluble zinc salt at a certain concentration.

[0023] The concentration of potassium hydroxide in the electrolyte of this invention is 0.1-10M.

[0024] The types of zinc salts in the electrolyte of this invention include zinc chloride, zinc sulfate, zinc nitrate, or zinc acetate.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] The high areal capacity phosphate cathode material derived from cobalt-nickel MOF of this invention is prepared by hydrothermal phosphate conversion using cobalt-nickel MOF as a precursor. The hydrothermal phosphate conversion process achieves the transformation of the precursor into cobalt-nickel phosphate, partially inheriting the porous and ordered three-dimensional open structure of cobalt-nickel MOF, exposing more active sites, and improving the diffusion rate of electrolyte ions inside the electrode. Furthermore, it generates additional cobalt-nickel phosphate on the surface of the cobalt-nickel MOF, which is beneficial for further improving the electrode's specific capacity. This invention achieves a 5 mA / cm² cathode material for the first time. 2 The cathode material exhibits a high areal capacity, achieving up to 10,000 s of single charge-discharge cycles at a given current density. The zinc-based alkaline battery system assembled with this material, a zinc anode, and an electrolyte demonstrates high capacity, good stability, and satisfactory electrochemical performance. The cobalt-nickel MOF-derived phosphate cathode material disclosed in this invention possesses ultra-high capacity, with a reduction peak-to-peak value reaching 160 mA / cm² at a scan rate of 15 mV / s. 2 Furthermore, the peak value of the reduction peak continuously increases with increasing scan rate; at 5 mA / cm 2 At current densities, a single charge-discharge process can reach 10,000 s, and the capacity of these peak conversions is significantly higher than that of materials prepared by other processes in the same field. Attached Figure Description

[0027] Figure 1 The samples prepared in Example 1 were Ni-MOF-1 and Ni-MOF-2 at 5 mA / cm 2 GCD plot at current density.

[0028] Figure 2 The sample prepared in Example 2 was NiCo-MOF-1 at 5 mA / cm 2 GCD plot at current density.

[0029] Figure 3 The sample prepared in Example 3 was Ni-MOF-3 at 5 mA / cm 2 GCD plot at current density.

[0030] Figure 4 The samples prepared in Example 4 were Ni-MOF-4 and Ni-MOF-5 at 5 mA / cm 2 GCD plot at current density.

[0031] Figure 5 The samples prepared in Example 5 were Ni-MOF-6 and Ni-MOF-7 at 5 mA / cm 2 GCD plot at current density.

[0032] Figure 6 The CV curves of the samples Ni-MOF-8, Ni-MOF-9 and Ni-MOF-10 prepared in Example 6 at a scan rate of 20 mV / s are shown.

[0033] Figure 7 The samples prepared in Example 7 were NiCo-MOF-11 and NiCo-MOF-12 at 5 mA / cm 2 GCD plot at current density.

[0034] Figure 8 The sample prepared in Example 8 was an aqueous zinc-cobalt-nickel battery assembled with NiCo-MOF-11 and commercial zinc sheets, operating at 40 mA / cm². 2 Cyclic stability plot at current density.

[0035] Figure 9 The CV curve of the sample prepared in Example 9 is NC-MOF@NCPi-1 at a scan rate of 15mV / s.

[0036] Figure 10 The samples prepared for Example 10 were NC-MOF@NCPi-2 and NC-MOF@NCPi-3 at 5 mA / cm 2 GCD plot at current density.

[0037] Figure 11 The sample prepared in Example 11 was an aqueous zinc-cobalt-nickel battery assembled with NC-MOF@NCPi-2 and commercial zinc sheets, operating at 40 mA / cm. 2 Cyclic stability plot at current density.

[0038] Figure 12 The sample prepared in Example 12 was an aqueous zinc-cobalt-nickel battery assembled with NC-MOF@NCPi-3 and commercial zinc sheets, operating at 40 mA / cm. 2 Cyclic stability plot at current density.

[0039] Figure 13 The sample prepared in Example 13 was NC-MOF@NCPi-4 at 5 mA / cm 2 GCD plot at current density.

[0040] Figure 14 The sample prepared in Example 14 was an aqueous zinc-cobalt-nickel battery assembled with NC-MOF@NCPi-4 and commercial zinc sheets, operating at 40 mA / cm. 2 Cyclic stability plot at current density. Detailed Implementation

[0041] The following examples are intended to further illustrate the present invention, but not to limit it.

[0042] Including but not limited to the embodiments described below, the electrode performance of all embodiments as positive electrode materials was tested in a three-electrode system. The three-electrode system used the electrode obtained in the embodiments, the carbon rod, and Hg / HgO as the working electrode, counter electrode, and reference electrode, respectively. 3M KOH solution was used as the electrolyte in the three-electrode test system. During the working electrode test, a 1cm depth was maintained. 2 The effective area is immersed in the electrolyte.

[0043] Example 1

[0044] Dissolve 1.6 mmol of nickel chloride hexahydrate and 1.6 mmol of terephthalic acid in 68 ml of a mixed solvent (N,N-dimethylacetamide / anhydrous ethanol / deionized water ratio of 15 / 1 / 1); after stirring thoroughly, transfer the mixture to a container filled with nickel foam (3×4 cm). 2 After assembling the high-pressure hydrothermal reactor, place it in an electric heating drying oven at 140℃ for 6 hours. After the reaction stops and cools to room temperature, open the high-pressure hydrothermal reactor, remove the nickel foam, rinse it three times with deionized water and anhydrous ethanol, and dry it to obtain the Ni-MOF precursor (labeled as Ni-MOF-1).

[0045] The method is the same as the steps above, except that the amount of terephthalic acid is adjusted to 0.8 mmol to prepare the Ni-MOF (labeled as Ni-MOF-2).

[0046] Figure 1 This is a three-electrode constant current charge-discharge curve diagram of Ni-MOF-1 and Ni-MOF-2 as positive electrode materials in Example 1. At 5 mA / cm²... 2At the given current density, Ni-MOF-1 requires 500 seconds to complete a full charge and discharge cycle, approximately twice that of Ni-MOF-2. The data indicates that, under the mixed solvent conditions given in Example 1, the electrode prepared with a molar ratio of nickel chloride hexahydrate to terephthalic acid of 1:1 exhibits superior performance compared to the electrode with a molar ratio of 2:1 (the time in the constant current charge-discharge curve is positively correlated with the electrode capacity).

[0047] Example 2

[0048] Dissolve 0.8 mmol of nickel chloride hexahydrate, 0.8 mmol of cobalt chloride hexahydrate, and 1.6 mmol of terephthalic acid in 68 ml of a mixed solvent (N,N-dimethylacetamide / anhydrous ethanol / deionized water ratio of 15 / 1 / 1); after stirring thoroughly, transfer the mixed solution to a container filled with nickel foam (3×4 cm). 2 After assembling the high-pressure hydrothermal reactor, place it in an electric heating drying oven at 140℃ for 6 hours. After the reaction stops and cools to room temperature, open the high-pressure hydrothermal reactor, remove the nickel foam, rinse it three times with deionized water and anhydrous ethanol, and dry it to obtain the NiCo-MOF precursor (labeled as NiCo-MOF-1).

[0049] Figure 2 The 5 mA / cm value corresponds to the electrode obtained in Example 2. 2 The three-electrode constant current charge-discharge curves at current density show that the time required for a complete charge and discharge process of NiCo-MOF-1 is approximately 540 s. In Example 2, the molar ratio of the total metal salts cobalt and nickel to terephthalic acid was maintained at 1:1. Comparing the constant current charge-discharge curves with those of Ni-MOF-1 in Example 1, the capacity of the cobalt-nickel MOF electrode with introduced cobalt ions is slightly better than that of the nickel MOF alone.

[0050] Example 3

[0051] Dissolve 2.8 mmol of nickel nitrate hexahydrate and 0.45 mmol of terephthalic acid in 64 ml of a mixed solvent (N,N-dimethylacetamide / anhydrous ethanol / deionized water ratio of 10 / 3 / 3); after stirring thoroughly, transfer the mixture to a container filled with nickel foam (3×4 cm). 2 After assembling the high-pressure hydrothermal reactor, place it in an electric heating drying oven at 125℃ for 9 hours. After the reaction stops and cools to room temperature, open the high-pressure hydrothermal reactor, remove the nickel foam, rinse it three times with deionized water and anhydrous ethanol, and dry it to obtain the Ni-MOF precursor (labeled as Ni-MOF-3).

[0052] Figure 3 This is a diagram showing the three-electrode constant current charge-discharge curves corresponding to the electrodes obtained in Example 3. At 5 mA / cm²...2 At the given current density, the Ni-MOF-3 electrode obtained when the molar ratio of nickel nitrate hexahydrate and terephthalic acid in 64 ml of mixed solvent is 56:9 requires approximately 3200 s to complete one charge and discharge process, which is much longer than the corresponding electrodes in Examples 1 and 2 (500-520 s). This indicates that the electrode prepared under the conditions given in Example 3 has better performance advantages.

[0053] Example 4

[0054] Dissolve 2.8 mmol of nickel nitrate hexahydrate and 0.45 mmol of terephthalic acid in 64 ml of a mixed solvent (N,N-dimethylacetamide / anhydrous ethanol volume ratio of 1 / 1); after stirring thoroughly, transfer the mixture to a container filled with nickel foam (3×4 cm). 2 After assembling the high-pressure hydrothermal reactor, place it in an electric heating drying oven at 125℃ for 9 hours. After the reaction stops and cools to room temperature, open the high-pressure hydrothermal reactor, remove the foamed nickel, rinse it three times with deionized water and anhydrous ethanol, and dry it to obtain the Ni-MOF precursor (labeled as Ni-MOF-4).

[0055] The method is the same as the steps above, except that the mixed solvent is changed to N,N-dimethylacetamide to prepare the obtained Ni-MOF precursor (labeled as Ni-MOF-5).

[0056] Figure 4 For Ni-MOF-4 and Ni-MOF-5 in Example 4, at 5 mA / cm 2 The constant current charge-discharge curves at the current density show that the time required for one complete charge and discharge process is 690 s and 240 s, respectively. This corresponds to the electrodes in Example 3. Figure 3 (3200s) Compared with Ni-MOF-4 and Ni-MOF-5, there is a significant decline in the constant current charge-discharge time, indicating that deionized water and anhydrous ethanol are indispensable in the sample preparation process.

[0057] Example 5

[0058] Dissolve 5.6 mmol of nickel nitrate hexahydrate and 0.45 mmol of terephthalic acid in 64 ml of a mixed solvent (N,N-dimethylacetamide / anhydrous ethanol / deionized water ratio of 10 / 3 / 3); after stirring thoroughly, transfer the mixture to a container filled with nickel foam (3×4 cm). 2 After assembling the high-pressure hydrothermal reactor, place it in an electric heating drying oven at 125℃ for 15 hours. After the reaction stops and cools to room temperature, open the high-pressure hydrothermal reactor, remove the nickel foam, rinse it three times with deionized water and anhydrous ethanol, and dry it to obtain the Ni-MOF precursor (labeled as Ni-MOF-6).

[0059] The method is the same as the steps above, except that the hydrothermal reaction time is changed to 24 hours to prepare Ni-MOF (labeled as Ni-MOF-7);

[0060] Figure 5 For Ni-MOF-6 and Ni-MOF-7 in Example 5, at 5 mA / cm 2 The constant current charge-discharge curves at current densities show that the time required for one complete charge and discharge process for Ni-MOF-6 and Ni-MOF-7 is 3800 s and 5900 s, respectively. Under the conditions given in Example 5, compared to Ni-MOF-6 and Ni-MOF-7, the electrode obtained under the 24-hour condition, by only changing the hydrothermal reaction time, exhibits better electrochemical performance.

[0061] Example 6

[0062] Dissolve 5.6 mmol of nickel nitrate hexahydrate and 0.45 mmol of terephthalic acid in 64 ml of a mixed solvent (N,N-dimethylacetamide / anhydrous ethanol / deionized water ratio of 10 / 3 / 3); after stirring thoroughly, transfer the mixture to a container filled with nickel foam (3×4 cm). 2 After assembling the high-pressure hydrothermal reactor, place it in an electric heating drying oven at 125℃ for 15 hours. After the reaction stops and cools to room temperature, open the high-pressure hydrothermal reactor, remove the foamed nickel, rinse it three times with deionized water and anhydrous ethanol, and dry it to obtain the Ni-MOF precursor (marked as Ni-MOF-8).

[0063] The method is the same as the steps above, except that the temperature of the hydrothermal reaction is changed to 155℃ to prepare the Ni-MOF (labeled as Ni-MOF-9).

[0064] The method is the same as above, except that the temperature of the hydrothermal reaction is changed to 185℃ to prepare Ni-MOF (labeled as Ni-MOF-10).

[0065] Figure 6 The figures show the cyclic voltammograms of Ni-MOF-8, Ni-MOF-9, and Ni-MOF-10 at a scan rate of 20 mV / s in Example 6. The peak current density of the reduction peak of the Ni-MOF-8 sample at this scan rate can reach 297.5 mA / cm². 2 Significantly greater than Ni-MOF-9 (201 mA / cm) 2 ) and Ni-MOF-10 (207mA / cm 2The above results indicate that, under the conditions given in Example 6, by simply changing the temperature of the hydrothermal reaction, the electrochemical performance of the resulting electrode decreases when the temperature is increased from 125°C to 155°C or 185°C (the peak current in the cyclic voltammetry curve is positively correlated with the electrochemical performance of the electrode).

[0066] Example 7

[0067] Dissolve 3.7 mmol of nickel nitrate hexahydrate, 1.9 mmol of cobalt nitrate hexahydrate, and 0.45 mmol of terephthalic acid in 64 ml of a mixed solvent (N,N-dimethylacetamide / anhydrous ethanol / deionized water ratio of 10 / 3 / 3); after stirring thoroughly, transfer the mixed solution to a container filled with nickel foam (3×4 cm). 2 After assembling the high-pressure hydrothermal reactor, place it in an electric heating drying oven at 125℃ for 15 hours. After the reaction stops and cools to room temperature, open the high-pressure hydrothermal reactor, remove the nickel foam, rinse it three times with deionized water and anhydrous ethanol, and dry it to obtain the NiCo-MOF precursor (labeled as NiCo-MOF-11).

[0068] The method is the same as the steps above, except that the amounts of nickel nitrate hexahydrate and cobalt nitrate hexahydrate are simultaneously changed to 2.8 mmol, resulting in NiCo-MOF (labeled as NiCo-MOF-12).

[0069] Figure 7 For NiCo-MOF-11 and NiCo-MOF-12 in Example 7, at 5 mA / cm 2 The constant current charge-discharge curves at current density show that the time required for a complete charge-discharge cycle of NiCo-MOF-12 (6072s) is slightly longer than that of NiCo-MOF-11 (5903s). However, NiCo-MOF-11 exhibits a higher charge-discharge voltage plateau. Therefore, under the given conditions in Example 7, changing the molar ratio of cobalt salt and nickel salt has no significant effect on improving electrode performance.

[0070] Example 8

[0071] The electrode material NiCo-MOF-11 obtained in Example 7 (with an effective area of ​​1×1cm) 2 ), commercial zinc sheets (effective area 2×2cm) 2 An aqueous zinc-cobalt-nickel battery was assembled using a 3M KOH solution containing saturated ZnCl2 as the positive electrode, negative electrode, and electrolyte, respectively.

[0072] The positive electrode material in this embodiment includes, but is not limited to, the corresponding electrode materials in Examples 1-7.

[0073] Figure 8An aqueous zinc-cobalt-nickel battery, assembled with NiCo-MOF-11 and zinc sheets as the positive and negative electrodes respectively, operates at 40 mA / cm². 2 Stability test results for charge / discharge at current density. NiCo-MOF-11 / / Zn battery at 40 mA / cm². 2 After 500 charge-discharge cycles at the current density, the battery can only retain 38% of its initial capacity, indicating that the cycle stability of the battery assembled with cobalt-nickel MOF as the positive electrode of the aqueous zinc-cobalt-nickel battery is not ideal.

[0074] Example 9

[0075] Dissolve 2.4 mmol of ammonium dihydrogen phosphate and 0.05 mol of urea in 80 ml of deionized water; after the solution is stirred evenly, transfer it to a container containing NiCo-MOF-12 (3×4 cm). 2 The high-pressure hydrothermal reactor was placed in the inner liner of the hydrothermal reactor and then placed in an electric heating drying oven at 120°C for 6 hours for constant temperature reaction. After cooling to room temperature, the foamed nickel substrate was removed and rinsed three times with anhydrous ethanol, deionized water and anhydrous ethanol respectively. After drying, the nickel-cobalt MOF-derived phosphate electrode material (labeled as NC-MOF@NCPi-1) was obtained.

[0076] Figure 9 The image shows the cyclic voltammetry curve of the electrode NC-MOF@NCPi-1 obtained in Example 9 at a scan rate of 15 mV / s. NC-MOF@NCPi-1 exhibits a cyclic voltammetry of 261.5 mA / cm². 2 The reduction peak current.

[0077] Example 10

[0078] Dissolve 0.7 mmol of potassium dihydrogen phosphate in 63 ml of a mixed solvent (ethylene glycol to deionized water ratio of 5 / 2), and transfer to a container containing NiCo-MOF-12 (3×4 cm). 2 The high-pressure hydrothermal reactor was placed in the inner liner of the hydrothermal reactor and then placed in an electric heating drying oven at 150°C for 3 hours for constant temperature reaction. After cooling to room temperature, the foamed nickel substrate was removed and rinsed three times with anhydrous ethanol, deionized water and anhydrous ethanol respectively. After drying, the cobalt-nickel MOF-derived phosphate electrode material (labeled as NC-MOF@NCPi-2) was obtained.

[0079] The method is the same as the steps above, except that the amount of potassium dihydrogen phosphate is adjusted to 2.2 mmol to prepare nickel-cobalt MOF-derived phosphate electrode material (labeled as NC-MOF@NCPi-3).

[0080] Figure 10 For NC-MOF@NCPi-2 and NC-MOF@NCPi-3 in Example 10, at 5mA / cm 2The three-electrode constant current discharge curves at current density show that NC-MOF@NCPi-2 exhibits a longer constant current charge-discharge time (5631s vs. 4604s), indicating that under the conditions given in Example 10, increasing the molar number of potassium dihydrogen phosphate is beneficial to improving the electrochemical performance of the prepared electrode.

[0081] Example 11

[0082] The electrode material NC-MOF@NCPi-2 obtained in Example 10 (with an effective area of ​​1×1cm) 2 ), commercial zinc sheets (effective area 2×2cm) 2 An aqueous zinc-cobalt-nickel battery was assembled using a 3M KOH solution containing saturated ZnCl2 as the positive electrode, negative electrode, and electrolyte, respectively.

[0083] The positive electrode material in this embodiment includes, but is not limited to, the corresponding electrode materials in Examples 1-10.

[0084] Figure 11 An aqueous zinc-cobalt-nickel battery, assembled with NC-MOF@NCPi-2 and zinc sheets as the positive and negative electrodes respectively, operates at 40 mA / cm². 2 Stability test results for charge / discharge at current density. NC-MOF@NCPi-2 / / Zn battery at 40mA / cm 2 After 2900 charge-discharge cycles at current density, only 45% of the initial capacity can be retained, indicating that the battery assembled with NC-MOF@NCPi-2 as the positive electrode of the aqueous zinc-cobalt-nickel battery exhibits good stability (the capacity retention rate is 75.8% after 500 cycles).

[0085] Example 12

[0086] The electrode material NC-MOF@NCPi-3 obtained in Example 10 (with an effective area of ​​1×1cm) 2 ), commercial zinc sheets (effective area 2×2cm) 2 An aqueous zinc-cobalt-nickel battery was assembled using a 3M KOH solution containing saturated ZnCl2 as the positive electrode, negative electrode, and electrolyte, respectively.

[0087] The positive electrode material in this embodiment includes, but is not limited to, the corresponding electrode materials in Examples 1-10.

[0088] Figure 12 An aqueous zinc-cobalt-nickel battery assembled with NC-MOF@NCPi-3 and zinc sheets as positive and negative electrodes respectively, operates at 40 mA / cm. 2 Stability test results for charge / discharge at current density. NC-MOF@NCPi-3 / / Zn battery at 40mA / cm 2After 2600 charge-discharge cycles at current density, only 41% of the initial capacity was retained, indicating that the battery assembled with NC-MOF@NCPi-3 as the positive electrode of the aqueous zinc-cobalt-nickel battery exhibits satisfactory stability (the capacity retention rate is 64% after 500 cycles).

[0089] Example 13

[0090] Dissolve 0.9 mmol of cobalt nitrate hexahydrate, 0.9 mmol of nickel nitrate hexahydrate, 1.2 mmol of ammonium dihydrogen phosphate, and 0.05 mol of urea in 80 ml of deionized water; after the solution is stirred evenly, transfer it to a container with a cobalt-nickel MOF (3×4 cm²). 2 The high-pressure hydrothermal reactor was placed in the inner liner of the hydrothermal reactor and then placed in an electric heating drying oven at 120°C for 8 hours of constant temperature reaction. After cooling to room temperature, the foamed nickel substrate was removed and rinsed three times with anhydrous ethanol, deionized water and anhydrous ethanol respectively. After drying, the cobalt-nickel MOF-derived phosphate electrode material (labeled as NC-MOF@NCPi-4) was obtained.

[0091] Figure 13 For the NC-MOF@NCPi-4 sample in Example 10, at 5 mA / cm 2 The constant current charge-discharge curves at current density show that the NC-MOF@NCPi-4 sample requires 11430s to complete one charge-discharge process, which is much longer than all the samples in Examples 1-12, demonstrating the extremely high capacity of the NC-MOF@NCPi-4 sample.

[0092] Example 14

[0093] The electrode material obtained in Example 13 (effective area 1×1cm) 2 ), commercial zinc sheets (effective area 2×2cm) 2 An aqueous zinc-cobalt-nickel battery was assembled using a 3M KOH solution containing saturated ZnCl2 as the positive electrode, negative electrode, and electrolyte, respectively.

[0094] The cathode material in this embodiment includes, but is not limited to, Examples 1-13.

[0095] Figure 14 For the NC-MOF@NCPi-4 / / Zn battery in Example 11, at 40mA / cm 2 The stability test results under constant current show that the coulombic efficiency of NC-MOF@NCPi-4 / / Zn remains close to 100% during charge and discharge, exhibiting extremely high conversion efficiency, and reaching as high as 2 mAh / cm³ in the initial cycling phase. 2The high areal capacity was observed. However, the capacity consistently declined throughout the cycling process, peaking at the start of the cycle, indicating that the NC-MOF@NCPi-4 / / Zn material exhibits unsatisfactory cycling stability (at 40 mA / cm²). 2 At the current density, the capacity retention rate after 4000 charge-discharge cycles is approximately 38%, and the capacity retention rate after 500 charge-discharge cycles is 60%.

Claims

1. A method for preparing high-capacity phosphate cathode materials derived from cobalt-nickel MOFs, characterized in that, Its preparation method includes the following steps: Step 1: Dissolve nickel salt, cobalt salt, and organic ligand in a mixed solution composed of N,N-dimethylacetamide, anhydrous ethanol, and deionized water. After stirring evenly, add the solution to a three-dimensional substrate and perform a hydrothermal reaction. Then wash and dry to obtain the NiCo-MOF precursor. The molar ratio of nickel salt, cobalt salt, and organic ligand is 0.5~5.6:0.5~5.6:1~4. Step 2: Dissolve cobalt salt, nickel salt, phosphate, and urea in water. After the solution is stirred evenly, add NiCo-MOF precursor and carry out hydrothermal reaction. Then wash and dry to obtain cobalt-nickel MOF-derived phosphate electrode material. The molar ratio of cobalt salt, nickel salt, phosphate, and urea is 0.1~0.9:0.1~0.9:0.5-2.4:0.01-0.

05. The cobalt salt includes any one of cobalt nitrate, cobalt chloride, cobalt sulfate, or cobalt acetate; the nickel salt includes any one of nickel nitrate, nickel chloride, nickel sulfate, or nickel acetate; the phosphate salt includes any one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, or disodium hydrogen phosphate; and the organic ligand is terephthalic acid.

2. The method for preparing the high-capacity phosphate cathode material derived from cobalt-nickel MOF according to claim 1, characterized in that, In step one, the volume ratio of N,N-dimethylacetamide, anhydrous ethanol, and deionized water is 8-10:1-4:0.1-1.

3. The method for preparing the high-capacity phosphate cathode material derived from cobalt-nickel MOF according to claim 1, characterized in that, In step one, the hydrothermal reaction temperature is 100℃~180℃, and the hydrothermal reaction time is 6h~24h.

4. The method for preparing the high-capacity phosphate cathode material derived from cobalt-nickel MOF according to claim 1, characterized in that, The three-dimensional substrate includes hydrophilic carbon paper, nickel foam, titanium alloy mesh, or stainless steel mesh.

5. The method for preparing the high-capacity phosphate cathode material derived from cobalt-nickel MOF according to claim 1, characterized in that, In step two, the urea concentration in the solution is 0.001-1M.

6. The method for preparing the high-capacity phosphate cathode material derived from cobalt-nickel MOF according to claim 1, characterized in that, In step two, the hydrothermal reaction temperature is 100℃~200℃, and the hydrothermal reaction time is 1~36h.

7. An aqueous zinc-based alkaline battery, characterized in that, The zinc-based alkaline battery comprises three parts: a phosphate positive electrode material, a zinc negative electrode material, and an electrolyte prepared by the method described in any one of claims 1-6.

8. The aqueous zinc-based alkaline battery according to claim 7, characterized in that, The electrolyte is a solution of potassium hydroxide and a saturated aqueous solution of soluble zinc salt, wherein the concentration of potassium hydroxide is 0.1-10M, and the aqueous solution of soluble zinc salt includes any one of zinc chloride, zinc sulfate, zinc nitrate, zinc acetate, or zinc oxide.

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